Employee Benefit Plans - Additional Information (Details) - USD ($)	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Supplemental executive retirement plan	$ 11,777,000	$ 11,337,000
Supplemental Executive Retirement Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Normal retirement age	65 years
Early retirement age	55 years
Vesting percentage under the plan for attaining age 55 and 10 years of service	100.00%
Defined benefit plan arrangement minimum age	55 years
Completed at least credited service period	10 years
Vesting percentage under the plan prior to attaining age 55 and 10 years of service	0.00%
Defined benefit plan employees minimum requisition period under specific conditions	5 years
Benefits payable targeted percentage	45.00%
Period in which the executive officer earned the highest salary and bonus	3 years
Employment period for computation of benefit	10 years
Eligible age under condition one for reduced benefits under the plan	62 years
Eligible service under condition one for reduced benefits under plan	10 years
Eligible age under condition two for reduced benefits under plan	55 years
Eligible service under condition two for reduced benefits under plan	25 years
Lump sum payment period	10 years
Supplemental executive retirement plan	$ 11,800,000	$ 11,300,000
Employer contributions to benefit plans	$ 0