Employee Benefits and Share-Based Compensation - Stock Option Activity (Details) - 2009 Plan - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Number of Shares
Outstanding at beginning of period (in shares)			3,214
Granted (in shares)			504
Exercised (in shares)			(668)
Expired (in shares)			(6)
Forfeited (in shares)			(79)
Outstanding at end of period (in shares)	2,965		2,965		3,214
Exercisable at end of period (in shares)	1,252		1,252
Vested and expected to vest at end of period (in shares)	2,965		2,965
Weighted Average Exercise Price
Outstanding beginning balance (in dollars per share)			$ 26.06
Granted (in dollars per share)			38.87
Exercised (in dollars per share)			21.66
Expired (in dollars per share)			27.53
Forfeited (in dollars per share)			32.54
Outstanding ending balance (in dollars per share)	$ 29.06		29.06		$ 26.06
Exercisable at end of period (in dollars per share)	22.36		22.36
Vested and expected to vest at end of period (in dollars per share)	$ 29.06		$ 29.06
Weighted-average remaining years, outstanding			7 years 4 months 24 days		7 years 3 months 18 days
Weighted-average remaining years, exercisable at end of period			5 years 6 months
Weighted-average remaining years, vested and expected to vest at at end of period			7 years 4 months 24 days
Aggregate Intrinsic Value
Aggregate intrinsic value, outstanding at end of period	$ 65,247		$ 65,247		$ 26,331
Aggregate intrinsic value, exercisable at end of period	35,915		35,915
Aggregate intrinsic value, vested and expected to vest at end of period	$ 65,247		$ 65,247
Employee Stock Option
Aggregate Intrinsic Value
Weighted-average fair value (in dollars per share)	$ 12.49	$ 10.32	$ 11.22	$ 8.82
Intrinsic value of options exercised	$ 6,800	$ 2,100	$ 14,600	$ 5,000
Unrecognized compensation cost of unvested stock options	$ 13,700		$ 13,700
Weighted average period of compensation cost not yet recognized (in years)			2 years 9 months 18 days