Fair Value Measurements - Change in Estimated Fair Values Calculated for Assets Valued on Recurring Basis Utilizing Level 3 Inputs (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014
Fair Value Disclosures [Abstract]
Balance at the beginning of the period	$ 4,825
Credit gain on available-for-sale securities included in Other income (expense), net	39
Unrealized gain included in Other comprehensive income (loss)	100
Balance at the end of the period	$ 4,964