Stockholders Equity - Additional Information (Details) $ in Thousands	1 Months Ended						3 Months Ended		54 Months Ended
	Aug. 31, 2018 shares	Mar. 31, 2018 shares	Jul. 31, 2017 shares	Jan. 31, 2017 shares	Nov. 30, 2014 shares	Apr. 30, 2014 shares	Mar. 31, 2019 USD ($) shares	Mar. 31, 2018 USD ($) shares	Mar. 31, 2019 shares	Dec. 31, 2018 shares
Class Of Stock [Line Items]
Treasury stock shares acquired (in shares)							616,796	414,327
Treasury stock shares acquired | $							$ 26,970	$ 20,789
Number of units held by noncontrolling interest holders							13,053,465		13,053,465	13,053,465
Group LP
Class Of Stock [Line Items]
Noncontrolling interests (as a percent)							22.00%		22.00%	22.00%
Class A Common Stock
Class Of Stock [Line Items]
Aggregate stock issuance (in shares)						15,263,653
Common stock, shares issued							49,457,698		49,457,698	47,031,095
Common stock, shares outstanding							47,414,787		47,414,787	45,604,980
Increase in shares outstanding	4,685,217	4,689,295	5,680,903	5,356,876	4,511,058				24,923,349
Number of shares of common stock to be issued upon exchange of a partnership unit							1		1
Class A Common Stock | Group LP
Class Of Stock [Line Items]
Common stock, shares outstanding							47,414,787		47,414,787	45,604,980
Class B Common Stock
Class Of Stock [Line Items]
Common stock, shares issued							10,493,358		10,493,358	10,493,358
Common stock, shares outstanding							10,493,358		10,493,358	10,493,358
Increase in shares outstanding						36,158,698
Ratio of subscription price to the initial public offering price of shares of common stock					0.00055
Dividends payable ratio to outstanding shares of publicly traded common stock					0.00055