Fair Value Measurements - Summary of Activity for Assets Measured at Fair Value Using Significant Unobservable Inputs (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2015 USD ($)
Fair Value Disclosures [Abstract]
Balance at December 31, 2014	$ 1,971
Total unrealized gains, excluding tax impact, included in other comprehensive loss	106
Balance at September 30, 2015	2,077
Total gains or losses for the period included in net loss attributable to the change in unrealized gains or losses relating to assets still held at the reporting date	$ 0