Employee Benefit Plans - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Pension
Defined Benefit Plan Disclosure [Line Items]
Prior service cost	$ 0	$ (13)
Net (losses) gains	(27,710)	(30,965)
Negative plan amendment	0	0
Deferred income tax benefit (expense)	1,927	2,425
AOCI	(25,783)	(28,553)
Postretirement
Defined Benefit Plan Disclosure [Line Items]
Prior service cost	0	0
Net (losses) gains	45	(90)
Negative plan amendment	0	0
Deferred income tax benefit (expense)	6	(22)
AOCI	$ 51	$ (112)