Summary of Significant Accounting Policies - Weighted Average Shares of Unvested Restricted Stock (Detail) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Unvested restricted stock	1,576	1,210	1,430	1,184