The 2012 annual 401(k) deferral limit for employees under age 50 was $17,000. Employees turning age 50 or over in 2012 could defer up to $22,500 in 2012. The Company makes matching contributions to the plan equal to 100% on the first 15% of employee deferred wages.

$ 11,400,000

$ 7,400,000

$ 8,700,000

Defined Contribution Benefit Plans [Line Items]

Maximum annual employee deferral

22,500

Defined Contribution Benefit Plans [Line Items]

Percentage of employee gross earnings employer makes matching contributions on for the non-qualified deferred compensation plan

15.00%

Retirement and Deferred Compensation Plans - Additional Information (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Retirement Plan
Defined Contribution Benefit Plans [Line Items]
Defined contribution plan description	The 2012 annual 401(k) deferral limit for employees under age 50 was $17,000. Employees turning age 50 or over in 2012 could defer up to $22,500 in 2012. The Company makes matching contributions to the plan equal to 100% on the first 15% of employee deferred wages.
Percentage matching contributions from employer on the first 15% of employee deferred wages	100.00%
Retirement plan expense	$ 11,400,000	$ 7,400,000	$ 8,700,000
Retirement Plan \| Employees under age 50 \| Maximum
Defined Contribution Benefit Plans [Line Items]
Maximum annual employee deferral	17,000
Retirement Plan \| Employees turning age 50 or more \| Maximum
Defined Contribution Benefit Plans [Line Items]
Maximum annual employee deferral	22,500
Deferred Compensation Plan
Defined Contribution Benefit Plans [Line Items]
Employer contributions to deferred compensation plan	$ 3,500,000	$ 3,100,000	$ 2,800,000
Deferred Compensation Plan \| Maximum
Defined Contribution Benefit Plans [Line Items]
Percentage of employee gross earnings employer makes matching contributions on for the non-qualified deferred compensation plan	15.00%