Related Party Transactions - Management Fees (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Related Party Transactions
Related party expenses		$ 267		$ 553
Vestar | Management Fees
Related Party Transactions
Related party expenses	$ 0	$ 267	$ 0	553
Vestar | Transaction Advisory Fee
Related Party Transactions
Transaction advisory fee				$ 8,500