Employee Benefit Plans (Details 4) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Deferred Compensation Plan
Liabilities, including the Company's common stock	$ 33,211,000	$ 23,893,000
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	6,900,000	6,300,000	5,600,000
Deferred compensation plan
Deferred Compensation Plan
Market value of the trust assets, excluding the Company's common stock	12,500,000	10,600,000
Liabilities, including the Company's common stock	33,200,000	23,900,000
Company's common stock held in the rabbi trust	5,700,000	5,700,000
Number of common stock deferred into the rabbi trust (in shares)	534,174
General and Administrative expense recognized due to increase in the closing price of the Company's shares held in the trust and also due to the sale of shares in the Company's stock	7,400,000
Plan contributions charged to expense	$ 742,605	$ 661,676	$ 522,807