Share-Based Compensation (Details 2) (USD $)	9 Months Ended
	Sep. 30, 2012
Restricted stock activity
Restricted shares outstanding, beginning of period, weighted average price	$ 31.89
Restricted shares outstanding, beginning of period, shares	834,703
Restricted shares granted, weighted average price	$ 31.50
Restricted shares granted, shares	529,050
Restricted shares canceled, weighted average price	$ 33.73
Restricted shares canceled, shares	(67,943)
Restricted shares vested, weighted average price	$ 26.48
Restricted shares vested, shares	(369,465)
Restricted shares outstanding, end of period, weighted average price	$ 33.69
Restricted shares outstanding, end of period, shares	926,345