Accumulated Other Comprehensive Income (Loss) (Rollforward of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Amounts reclassified from accumulated other comprehensive income	$ (19,828)	$ (14,256)	$ (8,306)
Pension and Postretirement Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance as of December 31, 2014	(22,870)
Other comprehensive income before reclassifications	3,305
Amounts reclassified from accumulated other comprehensive income	(19,828)
Change in accumulated other comprehensive income (loss)	23,133
Balance as of December 31, 2015	$ 263	$ (22,870)