Entity information:
Income Taxes
Income tax expense is comprised of the following amounts:
 
Year Ended December 31,
 
2017
 
2016
 
2015
 
(In Thousands)
Current provision:
 
 
 
 
 
Federal
$
27,825

 
$
22,954

 
$
23,340

State
5,013

 
5,116

 
4,774

Total current provision
32,838

 
28,070

 
28,114

Deferred provision:
 
 
 
 
 
Federal
10,209

 
2,271

 
679

State
589

 
51

 
560

Total deferred provision
10,798

 
2,322

 
1,239

Total provision for income taxes
$
43,636

 
$
30,392

 
$
29,353


Total provision for income taxes differed from the amounts computed by applying the statutory U.S. federal income tax rate 35.0% to income before tax expense as a result of the following:
 
Year Ended December 31,
 
2017
 
2016
 
2015
 
(Dollars In Thousands)
Expected income tax expense at statutory federal tax rate
$
34,039

 
$
29,965

 
$
28,603

State taxes, net of federal income tax benefit
3,641

 
3,358

 
3,467

Bank-owned life insurance
(364
)
 
(368
)
 
(367
)
Tax-exempt interest income
(873
)
 
(826
)
 
(622
)
Income attributable to noncontrolling interest in subsidiary
(870
)
 
(1,163
)
 
(994
)
Merger and acquisition expense
138

 
—

 
—

Tax Reform Act Adjustment
8,965

 
—

 
—

Investments in affordable housing projects
(653
)
 
(640
)
 
(526
)
Other, net
(387
)
 
66

 
(208
)
Total provision for income taxes
$
43,636

 
$
30,392

 
$
29,353

Effective income tax rate
44.9
%
 
35.5
%
 
35.9
%


The Company's effective tax rate was 44.9% as of December 31, 2017 compared to 35.5% as of December 31, 2016. The increase in the Company's effective tax rate from 2016 was primarily driven by $9.0 million related to the enactment of the Tax Reform Act and $138.0 thousand of nondeductible merger and acquisition expenses.
On December 22, 2017, the Tax Reform Act was enacted, which represents the most comprehensive reform to the U.S. tax code in over thirty years. The majority of the provisions of the Tax Reform Act takes effect on January 1, 2018. The Tax Reform Act lowers the Company’s federal tax rate from 35% to 21%. The Tax Reform Act also contains other provisions that may affect the Company currently or in future years. Among these are changes to the deductibility of meals and entertainment, the deductibility of executive compensation, accelerated expensing of depreciable property for assets placed in service after September 27, 2017 and before 2023, limits the deductibility of net interest expense, eliminated the corporate alternative minimum tax, limited net operating loss carryforwards to 80% of taxable income and other provisions.
As a result of the Tax Reform Act, management re-valued the carrying value of our net deferred tax asset and investments in low income housing tax credits. The impact of the Tax Reform Act resulted in a write down of the carrying balance of net deferred tax assets and investments in affordable housing projects of $8.6 million and $0.3 million, respectively.

The tax effects of temporary differences that give rise to significant portions of the deferred tax assets and liabilities at the dates indicated are as follows:
 
At December 31,
 
2017
 
2016
 
(In Thousands)
Deferred tax assets:
 
 
 
Allowance for loan and lease losses
$
15,618

 
$
21,655

Deferred compensation
1,032

 
5,659

Supplemental Executive Retirement Plans
2,805

 
4,127

Unrealized loss on investment securities available-for-sale
1,728

 
2,355

Net operating loss carryforwards
415

 
999

Postretirement benefits
400

 
465

Nonaccrual interest
551

 
621

Accrued expense
563

 
828

Restricted stock and stock option plans
621

 
573

Employee stock ownership plan
124

 
147

Other
67

 
61

Total gross deferred tax assets
23,924

 
37,490

Deferred tax liabilities:
 
 
 
Identified intangible assets and goodwill
2,778

 
4,660

Deferred loan origination costs, net
2,918

 
3,370

Depreciation
1,866

 
2,193

Prepaid expense
109

 
1,045

Acquisition fair value adjustments
1,192

 
975

Total gross deferred tax liabilities
8,863

 
12,243

Net deferred tax asset
$
15,061

 
$
25,247


As of December 31, 2017, the Company had net operating loss carryforwards for federal income tax purposes of $0.4 million which are available to offset future federal taxable income, if any, through 2020. According to Section 382 of the Internal Revenue Code, the net operating loss carryforwards and credit are subject to an annual limitation of $0.9 million.
The Company has determined that a valuation allowance is not required for any of its deferred tax assets because it believes that it is more likely than not that these assets will reverse against future taxable income.
For federal income tax purposes, the Company has a $1.8 million reserve for credit losses which remains subject to recapture. If any portion of the reserve is used for purposes other than to absorb the losses for which it was established, approximately 150% of the amount actually used (limited to the amount of the reserve) would be subject to taxation in the year in which used. As the Company intends to use the reserve only to absorb credit losses, no provision has been made for the $0.5 million liability that would result if 100% of the reserve were recaptured.
The Company did not have any unrecognized tax benefits accrued as income tax receivables or as deferred tax items as of December 31, 2017 and 2016. The Company files U.S. federal and state income tax returns. During the third quarter of 2017, the Company was notified by the Internal Revenue Service of its intent to examine the Company's 2015 consolidated federal income tax return. Management believes that this examination will conclude during the next 12 months. As of December 31, 2017, the Company is subject to examination by the Massachusetts, Rhode Island and several other state tax authorities for tax years after December 31, 2013.