Retirement Plans, Pension and Postretirement Plans Table (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Fair Value Of Plan Assets As A Percentage Of Net Benefit Obligation	167.00%	169.00%
Change in Fair Value of Plan Assets
Fair value of plan assets at beginning of year	$ 289,599
Fair value of plan assets at end of year	295,718	$ 289,599
Change in Benefit Obligation
Plan amendments	(1,759)	0	$ 0
Retirement Account Plan
Change in Fair Value of Plan Assets
Fair value of plan assets at beginning of year	289,599	303,496
Actual return on plan assets	17,097	495
Employer contributions	0	0
Gross benefits paid	(10,978)	(14,392)
Fair value of plan assets at end of year	295,718	289,599	303,496
Change in Benefit Obligation
Net benefit obligation at beginning of year	171,783	171,333
Service cost	6,780	11,257	11,058
Interest cost	7,121	6,617	7,132
Plan amendments	(823)	0
Actuarial (gain) loss	2,942	(3,032)
Gross benefits paid	(10,978)	(14,392)
Net benefit obligation at end of year	176,825	171,783	171,333
Funded (unfunded) status	118,893	117,816
Noncurrent assets	118,893	117,816
Current liabilities	0	0
Noncurrent liabilities	0	0
Asset (Liability) Recognized in the Consolidated Balance Sheets	118,893	117,816
Postretirement Plan
Change in Fair Value of Plan Assets
Fair value of plan assets at beginning of year	0	0
Actual return on plan assets	0	0
Employer contributions	248	264
Gross benefits paid	(248)	(264)
Fair value of plan assets at end of year	0	0	0
Change in Benefit Obligation
Net benefit obligation at beginning of year	3,436	3,578
Service cost	0	0	0
Interest cost	142	141	150
Plan amendments	(936)	0
Actuarial (gain) loss	9	(19)
Gross benefits paid	(248)	(264)
Net benefit obligation at end of year	2,403	3,436	$ 3,578
Funded (unfunded) status	(2,403)	(3,436)
Noncurrent assets	0	0
Current liabilities	(215)	(274)
Noncurrent liabilities	(2,188)	(3,162)
Asset (Liability) Recognized in the Consolidated Balance Sheets	$ (2,403)	$ (3,436)