Income Taxes - Federal Tax purpose (Details) - USD ($) $ in Thousands			3 Months Ended		12 Months Ended
	Jun. 30, 2018	Oct. 06, 2016	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
U.S. Federal income tax rate (as a percent)			21.00%
Deferred income taxes due to transfer of assets			$ 16,300
Deferred income tax expense from blended statutory income tax rates			$ 1,100
Effective tax rate			(588.40%)	33.60%
Current portion of liabilities under tax receivable agreement			$ 9,376		$ 9,446
Tax Receivable Agreement liability adjustment			8,477
Tax receivable agreement
Expected future tax benefits retained by the Company (as a percent)		15.00%
Reduction in tax receivable agreement liability due to reduction of future expected tax amortization			7,200
Reduction in tax receivable agreement liability due to change in state income tax rates			$ 1,100
Tax receivable agreement | CWGS, LLC
Units issued in exchange			5,725	173,286
Tax receivable agreement | Continuing Equity Owners and Crestview partners II GP LP
Payment, as percent of tax benefits (as a percent)		85.00%
CWH | CWGS, LLC
Ownership interest	41.90%		41.90%		41.90%
Units held			37,198,920		37,192,364
Crestview Partners II GP LP | Tax receivable agreement
Liability under tax receivable agreement			$ 125,700		$ 134,200
Current portion of liabilities under tax receivable agreement			$ 9,400