Summary of Potential Number of Shares Vesting under Restricted Stock Unit Awards (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2015 USD ($) shares
Schedule of Restricted Stock Unit [Line Items]
at IRR of at least 7.5% | shares	47,640
at IRR of at least 9.5% | shares	95,282
at IRR of at least 11.5% | shares	142,922
at IRR of at least 7.5%	$ 2,057
at IRR of at least 9.5%	4,115
at IRR of at least 11.5%	$ 6,173