Changes in Accumulated Other Comprehensive Loss by Component - Reclassifications (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Amounts reclassified from accumulated other comprehensive loss:
Interest expense, net									$ 15,195	$ 10,895	$ 8,129
Tax expense (benefit)									24,687	22,087	22,036
Reclassification net of tax	$ (10,101)	$ (7,302)	$ (16,328)	$ (5,278)	$ (15,141)	$ (15,548)	$ (13,104)	$ (383)	(38,469)	(43,572)	$ (39,352)
Other Postretirement Benefit Liability | Amount reclassified from accumulated other comprehensive income
Amounts reclassified from accumulated other comprehensive loss:
Actuarial (gains) losses									(127)	(68)
Tax expense (benefit)									48	24
Reclassification net of tax									(79)	(44)
Pension Liability | Amount reclassified from accumulated other comprehensive income
Amounts reclassified from accumulated other comprehensive loss:
Actuarial (gains) losses									724	1,020
Tax expense (benefit)									(275)	(367)
Reclassification net of tax									449	$ 653
Unrealized Net Loss on Interest Rate Swap | Interest rate swap | Amount reclassified from accumulated other comprehensive income
Amounts reclassified from accumulated other comprehensive loss:
Interest expense, net									390
Tax expense (benefit)									(148)
Reclassification net of tax									$ 242