Employee Benefits and Share-Based Compensation - Stock Option Activity (Details) - 2009 Plan [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Number of Shares
Outstanding at December 31, 2014 (in shares)			2,672
Granted (in shares)			200
Exercised (in shares)			(340)
Expired (in shares)			(2)
Forfeited (in shares)			(67)
Outstanding at June 30, 2015 (in shares)	2,463		2,463		2,672
Exercisable at June 30, 2015 (in shares)	1,425		1,425
Vested and expected to vest at June 30, 2015 (in shares)	2,435		2,435
Weighted Average Exercise Price
Outstanding at December 31, 2014 (in dollars per share)			$ 19.02
Granted (in dollars per share)			34.10
Exercised (in dollars per share)			15.54
Expired (in dollars per share)			15.57
Forfeited (in dollars per share)			23.30
Outstanding at June 30, 2015 (in dollars per share)	$ 20.60		20.60		$ 19.02
Exercisable at June 30, 2015 (in dollars per share)	16.46		16.46
Vested and expected to vest at June 30, 2015 (in dollars per share)	$ 20.50		$ 20.50
Weighted-average remaining years, outstanding (in years)			6 years 6 months		6 years 6 months
Weighted-average remaining years, exercisable at December 31, 2014 (in years)			4 years 10 months 24 days
Weighted-average remaining years, vested and expected to vest at June 30, 2015 (in years)			6 years 4 months 24 days
Aggregate Intrinsic Value, outstanding at June 30, 2015	$ 42,138		$ 42,138
Aggregate Intrinsic Value, exercisable at June 30, 2015	30,277		30,277
Aggregate Intrinsic Value, vested and expected to vest at June 30, 2015	$ 41,919		$ 41,919
Employee Stock Option [Member]
Weighted Average Exercise Price
Weighted-average fair value (in dollars per share)	$ 10.09	$ 9.00	$ 10.61	$ 8.29
Intrinsic value of options exercised	$ 4,300	$ 5,300	$ 6,700	$ 7,900
Unrecognized compensation cost of unvested stock options	$ 8,800		$ 8,800
Weighted average period of compensation cost recognized			2 years 8 months 12 days