Short-Term and Long-Term Investments - Amortized Cost and Estimated Fair Value of Available-for-Sale Securities by Contractual Maturities (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Available-for-sale Securities, Debt Maturities [Abstract]
Due in one year or less, Cost	$ 540
Due in two to ten years, Cost	170
Due in ten to twenty years, Cost	0
Due in twenty to forty years, Cost	6,000
Cost	6,710	6,820
Due in one year or less, Estimated Fair Value	541
Due in two to ten years, Estimated Fair Value	170
Due in ten to twenty years, Estimated Fair Value	0
Due in twenty to forty years, Estimated Fair Value	4,964
Estimated Fair Value	$ 5,675	$ 5,651