Stockholders' Equity - Net Income Attributable to Noncontrolling Interests (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Change In Ownership Interest [Line Items]
Net Income Attributable to Noncontrolling Interests	$ 523	$ 1,007	$ 3,400	$ 4,907
Noncontrolling interests	59,687		59,687		$ 57,826
Edgewater [Member]
Change In Ownership Interest [Line Items]
Net Income Attributable to Noncontrolling Interests	520	$ 1,007	3,397	$ 4,907
Noncontrolling interests	59,105		59,105		57,238
Other [Member]
Change In Ownership Interest [Line Items]
Net Income Attributable to Noncontrolling Interests	3		3
Noncontrolling interests	$ 582		$ 582		$ 588