Deferred Compensation (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Deferred Compensation Arrangements (Textual) [Abstract]
Additional compensation expense	$ 10,252,000	$ 1,529,000	$ 5,020,000
Year-over-year increase in market price of common stock, percent.	39.00%
Deferred compensation liability	$ 42,229,000	$ 32,428,000