Employee Benefit Plans (Details 4) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Deferred Compensation Plan
Liabilities, including the Company's common stock	$ 28,932,000	$ 33,211,000
Savings Investment Plan
Defined Contribution plans
Contribution match on portion of employee salary (as a percent)	6.00%
Discretionary profit sharing contribution Plan
Discretionary profit sharing contribution match on portion of employee salary and bonus (as a percent)	9.00%
Plan contributions charged to expense	7,200,000	6,900,000	6,300,000
Deferred compensation plan
Deferred Compensation Plan
Market value of the trust assets, excluding the Company's common stock	13,100,000	12,500,000
Liabilities, including the Company's common stock	28,900,000	33,200,000
Number of common stock deferred into the rabbi trust (in shares)	534,174
Company's common stock held in the rabbi trust	5,700,000	5,700,000
Plan contributions charged to expense	4,900,000
Company contributions to deferred compensation plan	$ 800,000	$ 700,000	$ 700,000