Stockholders' Equity - Net Income Attributable to Noncontrolling Interests (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Change In Ownership Interest [Line Items]
Net Income Attributable to Noncontrolling Interests	$ (566)	$ 1,969
Noncontrolling interests	70,151		$ 53,242
Profits Interest Participation Rights [Member]
Change In Ownership Interest [Line Items]
Noncontrolling interests	18,528		535
Edgewater [Member]
Change In Ownership Interest [Line Items]
Net Income Attributable to Noncontrolling Interests	(566)	1,968
Noncontrolling interests	51,610		52,695
Other [Member]
Change In Ownership Interest [Line Items]
Net Income Attributable to Noncontrolling Interests		$ 1
Noncontrolling interests	$ 13		$ 12