Income Taxes - Federal Tax purpose (Details) - USD ($) $ in Thousands			3 Months Ended		9 Months Ended		12 Months Ended
	Jun. 30, 2018	Oct. 06, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
U.S. Federal income tax rate (as a percent)				35.00%	21.00%		35.00%
Deferred tax expense					$ (1,400)		$ 118,400
Decrease in effective income tax rate			1.88%		(0.81%)
Increase in income tax receivable					$ 6,500
Increase in tax receivable agreement liability					2,000
Decrease in deferred tax assets					$ 2,200
Effective tax rate			19.20%	9.10%	17.30%	10.60%
Uncertain tax positions			$ 300		$ 300		0
Interest or penalties relating to income taxes			100	$ 0
Current portion of liabilities under tax receivable agreement			$ 10,404		$ 10,404		$ 8,093
Tax receivable agreement
Expected future tax benefits retained by the Company (as a percent)		15.00%
Tax receivable agreement | Continuing Equity Owners and Crestview partners II GP LP
Payment, as percent of tax benefits (as a percent)		85.00%
CWGS, LLC | Tax receivable agreement
Units issued in exchange					215,486	6,525,610
CWH | CWGS, LLC
Ownership interest	41.80%	22.60%			41.80%		41.50%
Units held			37,056,971		37,056,971		36,749,072
Crestview Partners II GP LP | Tax receivable agreement
Liability under tax receivable agreement			$ 133,700		$ 133,700		$ 137,700
Current portion of liabilities under tax receivable agreement			$ 10,400		$ 10,400		$ 8,100