Employee Benefit Plans - Components of Pension Plan and SERP Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Settlement charges	$ (4,500)	$ (4,300)
Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	2,940	3,279	$ 3,642
Expected return on plan assets, net of expenses	(3,876)	(4,571)	(4,396)
Special termination benefits	860	1,838
Settlement charges	3,345	2,021	2,302
Amortization of net loss	2,095	1,239	2,918
Total for defined benefit plans	5,364	3,806	4,466
SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	1,713	1,685	1,637
Special termination benefits	290	365
Settlement charges	1,121	2,279	1,083
Amortization of net loss	2,354	2,188	2,844
Total for defined benefit plans	$ 5,478	$ 6,517	$ 5,564