Fair Value Measurements - Summary of Activity for Assets Measured at Fair Value Using Significant Unobservable Inputs (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013
Fair Value Disclosures [Abstract]
Balance at December 31, 2012	$ 2,225
Total net unrealized losses, excluding tax impact, included in other comprehensive income	(186)
Balance at September 30, 2013	2,039
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