Retirement Plans, Pension and Postretirement Plans Table (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Change in Fair Value of Plan Assets
Fair value of plan assets at beginning of year	$ 303,496
Fair value of plan assets at end of year	289,599	$ 303,496
Pension Plan [Member]
Change in Fair Value of Plan Assets
Fair value of plan assets at beginning of year	303,496	282,000
Actual return on plan assets	495	15,255
Employer contributions	0	21,000
Gross benefits paid	(14,392)	(14,759)
Fair value of plan assets at end of year	289,599	303,496	$ 282,000
Change in Benefit Obligation
Net benefit obligation at beginning of year	171,333	154,624
Service cost	11,257	11,058	12,078
Interest cost	6,617	7,132	6,237
Actuarial (gain) loss	(3,032)	13,278
Gross benefits paid	(14,392)	(14,759)
Net benefit obligation at end of year	171,783	171,333	154,624
Funded (unfunded) status	117,816	132,163
Noncurrent assets	117,816	132,163
Current liabilities	0	0
Noncurrent liabilities	0	0
Asset (Liability) Recognized in the Consolidated Balance Sheets	117,816	132,163
Other Postretirement Benefit Plan [Member]
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	264	343
Gross benefits paid	(264)	(343)
Fair value of plan assets at end of year	0	0	0
Change in Benefit Obligation
Net benefit obligation at beginning of year	3,578	3,288
Service cost	0	0	0
Interest cost	141	150	142
Actuarial (gain) loss	(19)	483
Gross benefits paid	(264)	(343)
Net benefit obligation at end of year	3,436	3,578	$ 3,288
Funded (unfunded) status	(3,436)	(3,578)
Noncurrent assets	0	0
Current liabilities	(274)	(330)
Noncurrent liabilities	(3,162)	(3,248)
Asset (Liability) Recognized in the Consolidated Balance Sheets	$ (3,436)	$ (3,578)