Stock-Based Compensation (Details) (USD $)	3 Months Ended		1 Months Ended	3 Months Ended		12 Months Ended	1 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2013 Restricted Stock Awards	Mar. 31, 2012 Restricted Stock Awards	Mar. 31, 2013 Restricted Stock Awards Awarded in 2009 and 2010	Mar. 31, 2013 Stock options	Mar. 31, 2012 Stock options	Dec. 31, 2009 Stock options	Mar. 31, 2013 Stock options Awarded in 2009	Mar. 31, 2013 Stock options Awarded in 2009 item	Dec. 31, 2009 Stock options Awarded in 2009	Mar. 31, 2013 Plan
Share-Based Compensation
Number of shares authorized for grant										6,900,000
Number of shares of common stock exchanged for each award	1
Aggregate number of shares approved	4,875,833			2,365,465
Number of restricted stock units for which performance targets established (in shares)			178,335						150,000
Compensation expense	$ 2,300,000	$ 2,500,000		$ 800,000	$ 900,000
Unrecognized compensation cost related to the unvested awards	6,000,000			2,400,000
Weighted average period over which unrecognized compensation cost is expected to be recognized	2 years 3 months 18 days			2 years 3 months 18 days
Number of Shares
Granted and unvested, beginning of period (in shares)	1,141,666
Vested (in shares)	(28,333)
Granted (in shares)	178,335
Forfeited (in shares)	0
Total granted and unvested (in shares)	1,291,668
Approved for grant (in shares)	710,000
Total awarded and unvested, end of period (in shares)	2,001,668
Weighted Average Grant Date Fair Value
Total Granted and Unvested, beginning of period, weighted average grant date fair value (in dollars per share)	$ 18.12
Vested, weighted average grant date fair value (in dollars per share)	$ 15.49
Granted, weighted average grant date fair value (in dollars per share)	$ 19.30
Total Granted and Unvested, end of period, weighted average grant date fair value (in dollars per share)	$ 18.34
Aggregate Intrinsic Value
Total Granted and Unvested, beginning of period, aggregate intrinsic value	15,641,000
Vested, aggregate intrinsic value	521,000
Granted, aggregate intrinsic value	3,442,000
Total Granted and Unvested, aggregate intrinsic value	24,929,000
Approved for grant, aggregate intrinsic value	13,703,000
Total Awarded and Unvested, end of period, aggregate intrinsic value	38,632,000
Vesting schedule of outstanding unvested restricted stock awards
2013 (in shares)	868,333
2014 (in shares)	408,335
2015 (in shares)	150,000
2016 (in shares)	165,000
2017 (in shares)	410,000
Total (in shares)	2,001,668
Number of unvested stock awards that will vest subject to the satisfaction of service-based requirements (in shares)	245,000
Number of unvested stock awards that will vest subject to the satisfaction of service-based requirements and the achievement of performance metrics (in shares)	1,756,668
Term of Stock Options				10 years
Number of stock option awards subject to achievement of pre-tax income performance targets (in shares)						750,000	150,000
Number of Shares
Total Granted and Outstanding, beginning of period (in shares)				1,315,465
Granted (in shares)				150,000
Total granted and outstanding (in shares)				1,465,465
Approved for grant (in shares)				680,000
Total Awarded and Unvested, end of period (in shares)				2,145,465
Weighted Average Grant Date Fair Value
Total Granted and Outstanding, beginning of period, grant date value (in dollars per share)				$ 9.72
Granted, grant date value (in dollars per share)				$ 9.02
Total Granted and Outstanding, end of period, grant date value (in dollars per share)				$ 9.65
Weighted Average Exercise Price
Total granted and outstanding, beginning of period, weighted average exercise price (in dollars per share)				$ 18.91
Granted, weighted average exercise price (in dollars per share)				$ 20.33
Total Granted and Outstanding, weighted average exercise price (in dollars per share)				$ 19.06
Approved for grant, weighted average exercise price (in dollars per share)				$ 11.14
Total Awarded and Outstanding, end of period, weighted average exercise price (in dollars per share)				$ 16.55
Number of vested and exercisable options (in shares)				490,465
Vested and exercisable options, weighted average exercise price (in dollars per share)				$ 19.79
Number of unvested stock option awards that will vest subject to the satisfaction of service-based requirements (in shares)				592,500
Number of unvested stock option awards that will vest subject to the satisfaction of service-based requirements and the achievement of performance metrics (in shares)				1,062,500
Intrinsic value of outstanding options				$ 2,900,000
Weighted average remaining contractual term of outstanding options				6 years 3 months 18 days
Number of installments for vesting of stock awards								5
Key assumptions used in estimating the grant date fair values of stock option awards granted
Risk-free interest rate (as a percent)								0.48%
Expected life of options								3 years 7 months 6 days
Expected volatility of underlying stock (as a percent)								51.00%
Expected quarterly dividends (as a percent)								0.00%