Organization and Nature of Operations - Redemption of CW Units (Details) - $ / shares			1 Months Ended		3 Months Ended	6 Months Ended	12 Months Ended
	Mar. 20, 2019	Feb. 12, 2018	Mar. 31, 2019	Jul. 31, 2018	Jun. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Feb. 07, 2018
Redemptions of CW Units
CW Units held by legacy CW Unit Holders					28,020,000	28,020,000	37,236,000	60,558,000
CW Unit redemptions					700,000	(742,000)	(7,000)
IPO
Redemptions of CW Units
CW Unit redemptions		(12,118,000)
July 2018 follow-on offering
Redemptions of CW Units
CW Unit redemptions				(11,197,000)
March 2019 Secondary Offering
Redemptions of CW Units
CW Unit redemptions	8,500,000		(8,474,000)
Class A Common Stock
Organization and Nature of Operations
Common stock, par value					$ 0.01	$ 0.01	$ 0.01
Redemptions of CW Units
Redemption ratio, shares of common stock per unit redeemed					1	1
Class B Common Stock
Organization and Nature of Operations
Common stock, par value					$ 0.01	$ 0.01	$ 0.01