Office Closing and Termination Costs - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Restructuring Cost And Reserve [Line Items]
Termination costs	$ 5	$ 417	$ 8,400	$ 167	$ 6,367
Stock-based compensation expense (gain)					1,721
Building lease				$ 167	$ 3,232	$ 3,200
Oklahoma City Restructuring
Restructuring Cost And Reserve [Line Items]
Additional accruals for severance costs						275
Stock-based compensation expense (gain)						$ 608