Condensed Consolidated Statements of Comprehensive Income/(Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 40,207	$ 53,054	$ 88,090	$ 48,106
Other comprehensive income/(loss), net of taxes:
Interest rate swaps (net of $(0.2) million, $0.2 million, $(0.5) million and $0.6 million tax (expense)/benefit, respectively)	355	(274)	753	(897)
Qualified pension and post-employment benefit plans (net of $11.3 million, $0 million, $49.0 million and $0 million tax benefit, respectively)	(58,792)	(41,698)	(132,807)	573,635
Total other comprehensive income/(loss)	(58,437)	(41,972)	(132,054)	572,738
Comprehensive income/(loss)	$ (18,230)	$ 11,082	$ (43,964)	$ 620,844