Basis of Presentation of Interim Financial Information - Initial Public Offering (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	May. 31, 2015	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Initial Public Offering
IPO related costs incurred but not yet paid				$ 3,426
Equity‑based compensation				74,997	$ 4,907
Transaction advisory fee				8,500
Extinguishment of debt		$ 638	$ 2,886	638	$ 2,886
Transaction Advisory Fee | Vestar
Initial Public Offering
Transaction advisory fee				$ 8,500
IPO
Initial Public Offering
Equity‑based compensation	$ 70,400
IPO | Term Loan
Initial Public Offering
Extinguishment of debt	638
IPO | Transaction Advisory Fee | Vestar
Initial Public Offering
Transaction advisory fee	$ 8,500
IPO | Common
Initial Public Offering
Shares issued in offering	10,235
Share price (in dollars per share)	$ 25.00
Proceeds from the issuance of common stock in initial public offering, net of fees	$ 234,600
IPO related costs incurred but not yet paid	$ 3,400
IPO, excluding Underwriters' Option | Common
Initial Public Offering
Shares issued in offering	8,900
Underwriters' Option | Common
Initial Public Offering
Shares issued in offering	1,335