Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue	$ 171,977	$ 168,947	$ 166,898	$ 76,530	$ 72,939	$ 71,089	$ 67,372	$ 65,271	$ 584,352	$ 276,671	$ 263,937
Gross profit	116,430	104,638	109,365	39,195	38,291	39,422	37,025	36,729
Net loss	$ (2,003)	$ (12,751)	$ (8,857)	$ (23,370)	$ (232,216)	$ (12,355)	$ (9,715)	$ (10,448)	$ (10,551)	$ (264,734)	$ (26,944)
Common units
Basic and diluted net loss per common unit and Class B Unit (in dollars per unit)	$ 0.010	$ (0.10)	$ (0.060)						$ (0.43)
Class B Units
Basic and diluted net loss per common unit and Class B Unit (in dollars per unit)	$ (0.51)	$ (0.62)	$ (0.58)						$ (2.33)

$ 171,977

$ 168,947

$ 166,898

$ 76,530

$ 72,939

$ 71,089

$ 67,372

$ 65,271

$ 584,352

$ 276,671

$ 263,937

$ (2,003)

$ (12,751)

$ (8,857)

$ (23,370)

$ (232,216)

$ (12,355)

$ (9,715)

$ (10,448)

$ (10,551)

$ (264,734)

$ (26,944)

$ 0.010

$ (0.10)

$ (0.060)

$ (0.43)

$ (0.51)

$ (0.62)

$ (0.58)

$ (2.33)