| Schedule of Changes in Allowance for Sales Returns and Doubtful Accounts | Below is a summary of the changes in our allowance for sales returns. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | Years ended December 31, (in thousands) | Balance at beginning of year | 
 | Provision/adjustment | 
 | Write-off | 
 | Balance at  end of year | 
 |  | 2016 | $ | 4,431 | 
 | $ | 3,060 | 
 | $ | (4,787 | ) | $ | 2,704 | 
 |  | 2015 | 4,185 | 
 | 5,834 | 
 | (5,588 | ) | 4,431 | 
 |  | 2014 | 5,158 | 
 | 4,407 | 
 | (5,380 | ) | 4,185 | 
 | 
Below is a summary of the changes in our allowance for doubtful accounts.  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | Years ended December 31, (in thousands) | Balance at beginning of year | 
 | Provision/adjustment | 
 | Write-off | 
 | Balance at  end of year | 
 |  | 2016 | $ | 512 | 
 | $ | 499 | 
 | $ | (424 | ) | $ | 587 | 
 |  | 2015 | 354 | 
 | 699 | 
 | (541 | ) | 512 | 
 |  | 2014 | 455 | 
 | 777 | 
 | (878 | ) | 354 | 
 | 
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| Schedule of Changes in Deferred Sales Commission Costs | Below is a summary of the changes in our deferred sales commission costs included in prepaid expenses and other current assets. |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | Years ended December 31, (in thousands) | Balance at beginning of year | 
 | Additions | 
 | Expense | 
 | Balance at  end of year | 
 |  | 2016 | $ | 30,141 | 
 | $ | 37,553 | 
 | $ | (30,235 | ) | $ | 37,459 | 
 |  | 2015 | 22,630 | 
 | 55,934 | 
 | (48,423 | ) | 30,141 | 
 |  | 2014 | 20,088 | 
 | 24,615 | 
 | (22,073 | ) | 22,630 | 
 | 
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| Adoption of New Standard Impact on Previously Reported Quarterly Results | The following table summarizes the impact to our consolidated balance sheet, including the net amount charged to retained earnings as of January 1, 2016: |  |  |  |  |  |  |  |  | (dollars in thousands) | As of January 1, 2016 |  |   | Balance sheet location  | Amount |  | Decrease in deferred tax liabilities related to the cumulative effect adjustment from our election to recognize forfeitures as they occur rather than applying an estimated forfeiture rate | Deferred tax liability | $ | (606 | ) |  | Increase in additional paid-in capital resulting from our election to recognize forfeitures as they occur | Additional paid-in capital | $ | 1,540 | 
 |  | Net charge to retained earnings for cumulative effect adjustment from adoption of ASU 2016-09 | Retained earnings | $ | (934 | ) | 
The adoption of ASU 2016-09 impacted our previously reported quarterly results for fiscal year 2016 as follows: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | Consolidated balance sheets: |   |   |   |   |   |  | (dollars in thousands) | As of March 31, 2016 |   | As of June 30, 2016 |  |   | As Reported | As Adjusted |   | As Reported | As Adjusted |  | Additional paid-in capital | $ | 285,376 | 
 | $ | 285,606 | 
 |   | $ | 294,810 | 
 | $ | 294,019 | 
 |  | Retained earnings | $ | 134,192 | 
 | $ | 134,500 | 
 |   | $ | 136,338 | 
 | $ | 137,893 | 
 |  |   |   |   |   |   |   |  | Consolidated statements of comprehensive income: |   |   |   |   |   |  | (dollars in thousands, except per share amounts) | Three months ended  March 31, 2016 |   | Three months ended  June 30, 2016 |  |   | As Reported | As Adjusted |   | As Reported | As Adjusted |  | Income tax provision | $ | 2,664 | 
 | $ | 1,595 | 
 |   | $ | 3,598 | 
 | $ | 1,778 | 
 |  | Net income | $ | 4,995 | 
 | $ | 6,237 | 
 |   | $ | 7,813 | 
 | $ | 9,060 | 
 |  | Basic earnings per share | $ | 0.11 | 
 | $ | 0.14 | 
 |   | $ | 0.17 | 
 | $ | 0.20 | 
 |  | Diluted earnings per share | $ | 0.11 | 
 | $ | 0.13 | 
 |   | $ | 0.17 | 
 | $ | 0.19 | 
 |  | Diluted weighted average shares outstanding | 46,757,458 | 
 | 47,064,164 | 
 |   | 46,927,626 | 
 | 47,263,844 | 
 |  |   |   |   |   |   |   |  | Consolidated statements of cash flows: |   |   |   |   |   |  | (dollars in thousands) | Three months ended  March 31, 2016 |   | Six months ended  June 30, 2016 |  |   | As Reported | As Adjusted |   | As Reported | As Adjusted |  | Net cash provided by operating activities | $ | 104 | 
 | $ | 6,757 | 
 |   | $ | 37,987 | 
 | $ | 48,753 | 
 |  | Net cash provided by (used in) financing activities | $ | 9,546 | 
 | $ | 2,893 | 
 |   | $ | (13,852 | ) | $ | (24,618 | ) | 
 |