Employee Benefit Plans Schedule of Amounts Recognized in Other Comprehensive Income (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Changes in AOCL [Roll Forward]
Accumulated other comprehensive loss (Beginning Bal)				$ (96,350)
Amortization of prior service credit	[1]	$ (973)	$ (928)	(2,920)	$ (2,784)
Amortization of actuarial loss	[1]	1,452	1,798	4,145	5,393
Settlement cost	[1]	202	0	202	0
Accumulated other comprehensive loss (Ending Bal)		(117,913)		(117,913)
Pension Plan [Member]
Changes in AOCL [Roll Forward]
Accumulated other comprehensive loss (Beginning Bal)		(60,045)	(60,104)	(62,279)	(63,257)
Amortization of prior service credit		(45)	0	(135)	0
Amortization of actuarial loss		1,161	1,577	3,485	4,730
Settlement cost		202	0	202	0
Accumulated other comprehensive loss (Ending Bal)		(58,727)	(58,527)	(58,727)	(58,527)
Other Postretirement Benefit Plan [Member]
Changes in AOCL [Roll Forward]
Accumulated other comprehensive loss (Beginning Bal)		(5,433)	(3,110)	(3,945)	(1,696)
Amortization of prior service credit		(928)	(928)	(2,785)	(2,784)
Amortization of actuarial loss		291	221	660	663
Settlement cost		0	0	0	0
Accumulated other comprehensive loss (Ending Bal)		$ (6,070)	$ (3,817)	$ (6,070)	$ (3,817)

[1] See Note 6–Employee Benefit Plans for details of the changes in employee benefit plan assets and benefit obligations recognized in AOCL.