Office Closing and Termination Costs - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Restructuring Cost And Reserve [Line Items]
Termination costs	$ (77)	$ 8,371	$ 0	$ 6,290	$ 0
Additional accruals for severance costs				275
Stock-based compensation		2,999		1,720
Building lease		$ 0		3,156
Additional accruals for severance	$ 1,100			1,100
Oklahoma City Restructuring
Restructuring Cost And Reserve [Line Items]
Stock-based compensation				948
Other Restructuring
Restructuring Cost And Reserve [Line Items]
Stock-based compensation				$ 772