Employee Benefit Plans (Details) - Supplemental Executive Retirement Plan (SERP) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Supplemental Executive Retirement Plan Disclosure
Eligibility age	60 years
Number of months of salary taken as gross base for receipt of monthly payments	36 months
Vesting period of plan, when participants begin receiving payments	6 months
Reconciliation of beginning and ending balances of the projected benefit obligation
Projected benefit obligation at the beginning of the year	$ 57,955	$ 51,034
Service cost	3,518	5,517	$ 5,406
Interest cost	1,836	2,367	1,584
Plan amendments		3,862
Benefits paid	(7,117)
Actuarial gain	(1,379)	(4,825)
Projected benefit obligation at the end of the year	54,813	57,955	$ 51,034
Unfunded at end of the year	54,813	57,955
Current benefit obligation	14,700
Accumulated benefit obligation	42,300	$ 43,500
Future estimated benefit payments
2016	14,651
2019	4,580
2021-2025	51,836
Total future estimated benefit payments	$ 71,067