Share Based Compensation (Details Textual) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2011 Year Bank	Sep. 30, 2010	Sep. 30, 2011 Year Installment Bank	Sep. 30, 2010 Year
Employee Service Share Based Compensation Allocation of Recognized Period Costs (Textual)
Share-based compensation expenses			$ 9,281,000	$ 7,550,000
Grant date fair value of shares vested			$ 19.17	$ 12.60
Share-Based Compensation (Textual)
Share-based compensation	1,100,000	400,000	3,100,000	1,200,000
Shortfall in tax benefit			0	0
Net cash proceed from excise of stock options			1,100,000	900,000
Actual income tax benefit from excise of stock options			1,100,000	200,000
Look back period to estimate expected volatility of stock option grants			5.5	5.5
Intrinsic value of outstanding stock option	3,200,000		3,200,000
Intrinsic value of exercisable stock option	2,300,000		2,300,000
Intrinsic value of exercised stock option			4,200,000
Remaining contract life of outstanding stock option	6.0		6.0
Remaining contract life of exercisable stock option	4.4		4.4
General and Administrative Expense [Member]
Employee Service Share Based Compensation Allocation of Recognized Period Costs (Textual)
Share-based compensation expenses	3,200,000	2,400,000	8,800,000	6,900,000
Operating Lease Expense [Member]
Employee Service Share Based Compensation Allocation of Recognized Period Costs (Textual)
Share-based compensation expenses	100,000	100,000	200,000	300,000
Employee Stock Option [Member]
Employee Service Share Based Compensation Allocation of Recognized Period Costs (Textual)
Unrecognized compensation cost related to stock options	3,600,000		3,600,000
Weighted average recognition period of cost related to stock options			0.9
Restricted Stock [Member]
Employee Service Share Based Compensation Allocation of Recognized Period Costs (Textual)
Unrecognized compensation cost related to stock options	$ 18,900,000		$ 18,900,000
Weighted average recognition period of cost related to stock options			1.2
Grant date fair value of shares vested			$ 8.3