Share-Based Compensation (Details Textual) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Employee Service Share-based Compensation Allocation of Recognized Period Costs (Textual)
Look back period used to estimate expected volatility of stock option grants			5 years 6 months
Weighted average recognition period of cost related to options			1 year 0 months
Stockholders' Equity (Textual) [Abstract]
Net cash proceed from excise of stock options			$ 500,000	$ 1,100,000
Actual income tax benefit from excise of stock options			300,000	1,100,000
Share-based compensation expense			10,562,000	9,281,000
Share-based compensation (capitalized)	1,200,000	1,100,000	4,100,000	3,100,000
Intrinsic value of outstanding stock option	1,700,000		1,700,000
Remaining contract life of outstanding stock options.			6 years 1 month
Intrinsic value of exercisable stock option	1,700,000		1,700,000
Remaining contract life of exercisable stock option			4 years 9 months
Intrinsic value of exercised stock option			800,000
General and Administrative Expense [Member]
Stockholders' Equity (Textual) [Abstract]
Share-based compensation expense	3,200,000	3,200,000	9,900,000	8,800,000
Operating Lease Expense [Member]
Stockholders' Equity (Textual) [Abstract]
Share-based compensation expense	100,000	100,000	300,000	200,000
Employee Stock Option [Member]
Employee Service Share-based Compensation Allocation of Recognized Period Costs (Textual)
Unrecognized compensation cost related to stock options	4,200,000		4,200,000
Restricted Stock [Member]
Employee Service Share-based Compensation Allocation of Recognized Period Costs (Textual)
Unrecognized compensation cost related to stock options	19,200,000		19,200,000
Weighted average recognition period of cost related to options			1 year 2 months
Grant date fair value of shares vested			$ 9,800,000