Employee Benefit Plans - Additional Information (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
Historical compounded return on plan assets, minimum (in years)	10 years
Historical compounded return on plan assets, maximum (in years)	15 years
Defined contribution plans	$ 17,400	17,500	$ 16,400
Assets held in trust, current	42,800
Cash Surrender Value of Life Insurance	27,000	20,700
Deferred compensation	42,000	42,800
Rabbi Trust [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets held in trust, current	27,000
Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Assets held in trust, current	15,800
Defined Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement charges	(3,345)	(2,021)	(2,302)
Net actuarial loss during 2016	(2,100)
Company contributions	10,000
SERP [Member]
Defined Benefit Plan Disclosure [Line Items]
Settlement charges	(1,121)	(2,279)	$ (1,083)
Net actuarial loss during 2016	(2,100)
Company contributions	2,669	$ 4,845
Expected contributions to SERP	$ 17,500