Stock-Based Compensation (Details) (USD $)	3 Months Ended		1 Months Ended	3 Months Ended		1 Months Ended	3 Months Ended						1 Months Ended
	Mar. 31, 2014 Restricted Stock Unit Awards	Mar. 31, 2013 Restricted Stock Unit Awards	Mar. 31, 2014 Restricted Stock Unit Awards Awarded in 2014, 2013 and 2012	Mar. 31, 2014 Stock options	Mar. 31, 2013 Stock options	Mar. 31, 2014 Stock options Awarded in 2014, 2013 and 2012	Mar. 31, 2014 Stock options Awarded in 2014 - 1	Mar. 31, 2014 Stock options Awarded in 2014 - 2	Mar. 31, 2014 Stock options Awarded in 2014 - 3	Mar. 31, 2014 Stock options Awarded in 2014 - 4	Mar. 31, 2014 Stock options Awarded in 2014 - 5	Mar. 31, 2014 Plan	Mar. 31, 2014 Plan Stock options
Share-Based Compensation
Number of shares authorized for grant												6,900,000
Number of shares available for future grant (in shares)												75,461
Number of shares of common stock exchanged for each award	1
Aggregate number of shares approved	5,498,333			2,785,465
Number of restricted stock units for which performance targets are established (in shares)			866,500
Compensation expense	$ 3,900,000	$ 2,300,000		$ 1,500,000	$ 800,000
Unrecognized compensation cost related to the unvested awards	22,300,000			12,100,000
Weighted average period over which unrecognized compensation cost is expected to be recognized	3 years 1 month 6 days			3 years 3 months 18 days
Number of Shares
Granted and unvested, beginning of period (in shares)	361,668
Vested (in shares)	(161,668)
Granted (in shares)	866,500
Total granted and unvested (in shares)	1,066,500
Approved for grant (in shares)	401,000
Total awarded and unvested, end of period (in shares)	1,467,500
Weighted Average Grant Date Fair Value
Total Granted and Unvested, beginning of period, weighted average grant date fair value (in dollars per share)	$ 17.30
Vested, weighted average grant date fair value (in dollars per share)	$ 19.30
Granted, weighted average grant date fair value (in dollars per share)	$ 27.33
Total Granted and Unvested, end of period, weighted average grant date fair value (in dollars per share)	$ 25.15
Aggregate Intrinsic Value
Total Granted and Unvested, beginning of period, aggregate intrinsic value	9,512,000
Vested, aggregate intrinsic value	4,619,000
Granted, aggregate intrinsic value	24,843,000
Total Granted and Unvested, aggregate intrinsic value	30,577,000
Approved for grant, aggregate intrinsic value	11,497,000
Total Awarded and Unvested, end of period, aggregate intrinsic value	42,073,000
Vesting schedule of outstanding unvested restricted stock awards
2014 (in shares)	125,000
2015 (in shares)	342,500
2016 (in shares)	202,500
2017 (in shares)	752,500
2018 (in shares)	36,000
2019 (in shares)	9,000
Total (in shares)	1,467,500
Number of unvested stock awards that will vest subject to the satisfaction of service-based requirements (in shares)	150,000
Number of unvested stock awards that will vest subject to the satisfaction of service-based requirements and the achievement of performance metrics (in shares)	1,317,500
Term of Stock Options				10 years
Number of stock option awards subject to achievement of pre-tax income performance targets (in shares)						714,000
Number of Shares
Total Granted and Outstanding, beginning of period (in shares)				1,295,000
Granted (in shares)				714,000									250,000
Total granted and outstanding (in shares)				2,009,000
Approved for grant (in shares)				336,000
Total Awarded and Unvested, end of period (in shares)				2,345,000
Weighted Average Grant Date Fair Value
Total Granted and Outstanding, beginning of period, grant date value (in dollars per share)				$ 9.94
Granted, grant date value (in dollars per share)				$ 17.69
Total Granted and Outstanding, end of period, grant date value (in dollars per share)				$ 12.70
Weighted Average Exercise Price
Total granted and outstanding, beginning of period, weighted average exercise price (in dollars per share)				$ 20.20
Granted, weighted average exercise price (in dollars per share)				$ 18.40
Total Granted and Outstanding, weighted average exercise price (in dollars per share)				$ 19.56
Approved for grant, weighted average exercise price (in dollars per share)				$ 11.88
Total Awarded and Outstanding, end of period, weighted average exercise price (in dollars per share)				$ 18.46
Number of vested and exercisable stock options (in shares)				1,155,000
Vested and exercisable stock options, weighted average exercise price (in dollars per share)				$ 20.67
Number of unvested stock option awards that will vest subject to the satisfaction of service-based requirements (in shares)				495,000
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)				1,850,000
Intrinsic value of outstanding stock options				$ 18,300,000
Weighted average remaining contractual term of outstanding stock options				6 years 7 months 6 days
Key assumptions used in estimating the grant date fair values of stock option awards granted
Number of options for which fair value assumptions used							250,000	75,000	9,000	150,000	230,000
Risk-free interest rate (as a percent)							2.08%	1.72%	2.25%	1.46%	1.82%
Expected life of options							6 years 6 months	5 years 3 months 18 days	7 years	4 years 7 months 6 days	5 years 7 months 6 days
Expected volatility of underlying stock (as a percent)							50.97%	51.72%	50.68%	47.69%	51.86%
Expected quarterly dividends (per share)							$ 0.00	$ 0.00	$ 0.00	$ 0.00	$ 0.00