Share-Based Compensation (Details Textual) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 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 4 months
Stockholders' Equity (Textual) [Abstract]
Net cash proceed from excise of stock options			$ 400,000	$ 1,000,000
Actual income tax benefit from excise of stock options			200,000	1,100,000
Share-based compensation expenses			7,181,000	5,939,000
Share-based compensation (capitalized)	1,500,000	1,000,000	2,900,000	2,000,000
Intrinsic value of outstanding stock option	1,200,000		1,200,000
Remaining contract life of outstanding stock options.			6 years 4 months
Intrinsic value of exercisable stock option	1,200,000		1,200,000
Remaining contract life of exercisable stock option			4 years 11 months
Intrinsic value of exercised stock option			700,000
General and Administrative Expense [Member]
Stockholders' Equity (Textual) [Abstract]
Share-based compensation expenses	3,300,000	3,100,000	6,700,000	5,600,000
Operating Lease Expense [Member]
Stockholders' Equity (Textual) [Abstract]
Share-based compensation expenses	100,000	100,000	200,000	200,000
Employee Stock Option [Member]
Employee Service Share-based Compensation Allocation of Recognized Period Costs (Textual)
Unrecognized compensation cost related to stock options	5,200,000		5,200,000
Restricted Stock [Member]
Employee Service Share-based Compensation Allocation of Recognized Period Costs (Textual)
Unrecognized compensation cost related to stock options	23,600,000		23,600,000
Weighted average recognition period of cost related to options			1 year 5 months
Grant date fair value of shares vested			$ 9,200,000