Investments - Cost and Fair Value of Debt Investments Based on Maturities (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Available For Sale Securities Debt Maturities [Abstract]
Due in one year or less, Amortized Costs	$ 43,073	$ 32,536
Due within two years, Amortized Costs	39,084	49,558
Total, Amortized Costs	82,157	82,094
Due in one year or less, Fair Value	43,129	32,538
Due within two years, Fair Value	39,104	49,593
Total, Fair Value	$ 82,233	$ 82,131