Summary of Potential Number of Shares Vesting under Restricted Stock Unit Awards (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended
	Jun. 30, 2014
Schedule of Restricted Stock Unit [Line Items]
Number of shares vesting at IRR level of at least 8.5%	65,832
Number of shares vesting at IRR level of at least 10.5%	131,683
Number of shares vesting at IRR level of at least 12.5%	197,515
Fair value of shares vesting at IRR level of at least 8.5%	$ 1,879
Fair value of shares vesting at IRR level of at least 10.5%	3,758
Fair value of shares vesting at IRR level of at least 12.5%	$ 5,637