Slicers (applies to each fact value in each table cell)

Reporting Entity [Axis]

0000846617 (http://www.sec.gov/CIK)

Employee benefits	Period [Axis]
	2016-01-01 - 2016-12-31		2015-01-01 - 2015-12-31		2014-01-01 - 2014-12-31
	Defined Benefit Plans and Other Postretirement Benefit Plans [Axis]		Defined Benefit Plans and Other Postretirement Benefit Plans [Axis]		Defined Benefit Plans and Other Postretirement Benefit Plans [Axis]
	Pension Benefits	SERP Benefits	Pension Benefits	SERP Benefits	Pension Benefits	SERP Benefits
Weighted average assumptions used to determine benefit obligations:
Discount rate (as a percent)	4.05%	4.01%	4.30%	4.20%	3.90%	3.80%
Rate of compensation increase (as a percent)	3.00%	5.00%	3.00%	5.00%	3.00%	5.00%
Weighted average assumptions used to determine net periodic benefit cost:
Discount rate (as a percent)	4.30%	4.20%	3.90%	3.80%	4.90%	4.70%
Rate of compensation increase (as a percent)	3.00%	5.00%	3.00%	5.00%	3.00%	5.00%
Expected long-term rate of return (as a percent)	7.50%	xsi:nil	7.50%	xsi:nil	7.50%	xsi:nil