Summary of Potential Number of Shares Vesting under Restricted Stock Unit Awards (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2019 USD ($) shares
Disclosure Of Restricted Stock Unit [Abstract]
Number of shares vesting at IRR of at least 6% | shares	136,285
Number of shares vesting at IRR of at least 8% | shares	204,427
Number of shares vesting at IRR of at least 14% | shares	306,651
Value at grant at IRR of at least 6% | $	$ 5,011
Value at grant at IRR of at least 8% | $	7,517
Value at grant at IRR of at least 14% | $	$ 11,276