Employee Benefit Plans (Details)	12 Months Ended
	Dec. 31, 2015 USD ($) Contribution	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Tax-exempt interest earned on the life insurance policies	$ 1,908,000	$ 1,881,000	$ 1,856,000
Executive Officers [Member] | Executive Retirement Plan and Life Insurance Arrangements [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Employer contribution	3,500,000	2,700,000	2,700,000
Total accrued liability	31,300,000	27,300,000
Tax-exempt interest earned on the life insurance policies	1,908,000	1,881,000	1,856,000
Cash surrender value of life insurance policies	55,900,000	54,000,000
Senior Level Employees [Member] | Senior Management Retention Plan [Member]
Deferred Compensation Arrangement with Individual, Excluding Share-based Payments and Postretirement Benefits [Line Items]
Employer contribution	530,000	475,000	536,000
Total accrued liability	$ 2,300,000	1,500,000
Pension Plan [Member] | Profit Sharing Plan [Member]
Defined Contribution Plan Disclosure [Line Items]
Minimum requisite service period	1 year
Number of annual employer contribution | Contribution	2
Employer discretionary contribution amount	$ 925,000	875,000	825,000
Employer mandatory contributions amount	$ 1,100,000	$ 1,000,000	$ 952,000
Annual vesting percentage, first year	0.00%
Annual vesting percentage, full year thereafter	25.00%
Benefit vesting period	5 years