Share-base Compensation - Narrative (Details) (USD $)	12 Months Ended														12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Stock Options [Member]	Dec. 31, 2011 Stock Options [Member]	Dec. 31, 2010 Stock Options [Member]	Dec. 31, 2012 Restricted Stock [Member]	Dec. 31, 2011 Restricted Stock [Member]	Dec. 31, 2010 Restricted Stock [Member]	Dec. 31, 2012 Omnibus Incentive Plan 2009 [Member]	Dec. 17, 2009 Omnibus Incentive Plan 2009 [Member]	Dec. 17, 2009 Omnibus Incentive Plan 2009 [Member] Stock Options [Member]	Dec. 17, 2009 Omnibus Incentive Plan 2009 [Member] Share Awards Other than Stock Options [Member]	Dec. 31, 2012 Omnibus Incentive Plan 2009 [Member] Performance Shares [Member]	Dec. 31, 2012 Minimum [Member] Stock Options [Member]	Dec. 31, 2012 Maximum [Member] Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares authorized for grant											2,885,907	1,076,555
Number of shares authorized per participant annually												627,990	627,990
Annual authorized cash award per participant, maximum											$ 5,000,000
Number of shares available for grant										1,292,832				10,138
Vesting period															3 years	5 years
Options granted, grant date fair value per share	$ 17.66	$ 11.37	$ 8.05
Unrecognized compensation cost related to stock options				4,500,000
Weighted average period for recognition of compensation consts				2 years 8 months 12 days			1 year 10 months 24 days
Total compensation expense recognized				1,300,000	400,000	800,000	3,300,000	200,000	2,000,000
Tax benefit recognized from compensation expense				300,000	0	300,000	1,300,000	100,000	800,000
Aggregate fair value of shares vested							2,200,000	0	2,000,000
Unrecognized compensation cost with respect to restricted stock							$ 10,500,000