Long-Term Debt - Senior Secured Credit Facilities (Details) - USD ($) $ in Thousands			1 Months Ended	12 Months Ended
	Nov. 08, 2016	Sep. 21, 2016	Jun. 30, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Nov. 20, 2013
Long-Term Debt
Unamortized discount				$ 6,300	$ 4,900
Cash distribution to members		$ 100,000		$ 236,146	228,894	$ 60,101
Secured Debt | Line of Credit | Previous Senior Secured Credit Facility
Long-Term Debt
Maximum borrowing capacity							$ 545,000
Secured Debt | Line of Credit | Previous Senior Secured Credit Facility, Term Loan Facility
Long-Term Debt
Maximum borrowing capacity		828,200					525,000
Unamortized discount							$ 5,300
Original issue discount (as a percentage)							1.00%
Maximum borrowing capacity, increase in capacity		135,000	$ 95,000		$ 55,000	$ 117,000
Original issue discount from increase in capacity		$ 16,500
Secured Debt | Line of Credit | New Senior Secured Credit Facility
Long-Term Debt
Maximum borrowing capacity	$ 680,000
Secured Debt | Line of Credit | New Senior Secured Credit Facility Term Loan Facility
Long-Term Debt
Maximum borrowing capacity	$ 645,000
Term	7 years
Secured Debt | Revolving Credit Facility | Previous Senior Secured Credit Facility, Revolving Credit Facility
Long-Term Debt
Maximum borrowing capacity							$ 20,000
Secured Debt | Revolving Credit Facility | New Senior Secured Credit Facility Revolving Credit Facility
Long-Term Debt
Maximum borrowing capacity	$ 35,000
Term	5 years