Investments and Fair Value Measurements - Schedule of Unrealized Gains, Losses, and Fair Value of Held-to-maturity Investments (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Investments, Debt and Equity Securities [Abstract]
Held-to-maturity cost or amortized cost	$ 12,224	$ 11,748
Held-to-maturity gross unrealized gains	80	20
Held-to-maturity gross unrealized losses	(650)	(1,459)
Held-to-maturity fair value	$ 11,654	$ 10,309