Employee Equity-Based Compensation - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Equity-based compensation expense	$ 2,881	$ 3,409	$ 6,278	$ 9,011
Unrecognized equity-based compensation cost	19,500		19,500
Shares issuable upon the release of restricted stock awards
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Unrecognized equity-based compensation cost, restricted stock units	300		300
Performance-based stock options
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Equity-based compensation expense			$ 100
Contractual life			10 years
Granted (shares)					225,000
Performance-based stock options | Minimum
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Vesting period			1 year
Performance-based stock options | Minimum | Granted in 2018
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Vesting period			5 years
Performance-based stock options | Maximum
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Vesting period			2 years
Performance-based stock options | Maximum | Granted in 2018
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Vesting period			6 years
Property and equipment
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Equity-based compensation expense	$ 200	$ 100	$ 400	$ 500