Equity-Based Compensation - Stock Options Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Number of Shares
Outstanding at December 31, 2017 (in shares)			908,919
Granted (in shares)	0	0	0	0
Exercised (in shares)	(4,167)	(2,083)	(4,167)	(26,935)
Forfeited (in shares)			(918)
Expired (in shares)			(1,838)
Outstanding at June 30, 2018 (in shares)	901,996		901,996		908,919
Exercisable at June 30, 2018 (in shares)	855,446		855,446
Weighted Average Exercise Price
Outstanding at December 31, 2017, (in dollars per share)			$ 28.46
Granted (in dollars per share)			0.00
Exercised (in dollars per share)			14.65
Forfeited (in dollars per share)			31.30
Expired (in dollars per share)			31.30
Outstanding at June 30, 2018, (in dollars per share)	$ 28.52		28.52		$ 28.46
Exercisable at June 30, 2018 (in dollars per share)	$ 27.38		$ 27.38
Aggregate Intrinsic Value (in thousands)
Outstanding at June 30, 2018, aggregate intrinsic value	$ 3,692		$ 3,692		$ 7,008
Exercisable at June 30, 2018, aggregate intrinsic value	$ 3,692		$ 3,692
Weighted Average Remaining Contractual Term in Years
Outstanding at June 30, 2018, weighted average remaining contractual term in years			5 years 3 months		6 years 1 month
Exercisable at June 30, 2018, weighted average remaining contractual term in years			5 years 2 months