Employee Benefit Plans - Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension
Defined Benefit Plan Disclosure [Line Items]
Net (losses) gains	$ (477)	$ (37,559)	$ 60,171
Prior service cost	0	0	0
Negative plan amendment	0	0	0
Amortization of losses	3,733	6,542	20,914
Amortization of prior service cost	13	576	1,356
Amortization of negative plan amendment	0	0	0
Postretirement
Defined Benefit Plan Disclosure [Line Items]
Net (losses) gains	123	(2,250)	3,206
Prior service cost	0	0	0
Negative plan amendment	0	0	3,372
Amortization of losses	12	288	675
Amortization of prior service cost	0	8	66
Amortization of negative plan amendment	$ 0	$ (137)	$ (105)