Employee Benefits and Share-Based Compensation - Stock Option Activity (Details) - 2009 Plan - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Number of Shares
Outstanding at December 31, 2015 (in shares)			2,688
Granted (in shares)			443
Exercised (in shares)			(228)
Expired (in shares)			(4)
Forfeited (in shares)			(73)
Outstanding at June 30, 2016 (in shares)	2,826		2,826		2,688
Exercisable at June 30, 2016 (in shares)	1,391		1,391
Vested and expected to vest at June 30, 2016 (in shares)	2,660		2,660
Weighted Average Exercise Price
Outstanding at December 31, 2015 (in dollars per share)			$ 22.89
Granted (in dollars per share)			28.14
Exercised (in dollars per share)			18.22
Expired (in dollars per share)			27.58
Forfeited (in dollars per share)			28.68
Outstanding at June 30, 2016 (in dollars per share)	$ 23.94		23.94		$ 22.89
Exercisable at June 30, 2016 (in dollars per share)	18.85		18.85
Vested and expected to vest at June 30, 2016 (in dollars per share)	$ 23.61		$ 23.61
Weighted-average remaining years, outstanding (in years)			7 years 15 days		6 years 10 months 20 days
Weighted-average remaining years, exercisable at June 30, 2016 (in years)			5 years 1 month 10 days
Weighted-average remaining years, vested and expected to vest at June 30, 2016 (in years)			6 years 10 months 28 days
Aggregate Intrinsic Value, outstanding at June 30, 2016	$ 29,422		$ 29,422
Aggregate Intrinsic Value, exercisable at June 30, 2016	21,400		21,400
Aggregate Intrinsic Value, vested and expected to vest at June 30, 2016	$ 28,558		$ 28,558
Employee Stock Option
Weighted Average Exercise Price
Weighted-average fair value (in dollars per share)	$ 9.03	$ 10.09	$ 8.59	$ 10.61
Intrinsic value of options exercised	$ 2,200	$ 4,300	$ 2,900	$ 6,700
Unrecognized compensation cost of unvested stock options	$ 10,700		$ 10,700
Weighted average period of compensation cost recognized			2 years 11 months 12 days