Marketable Securities Scheduled Maturities of Available-for-Sale Debt Securities (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Due within one year, amortized cost	$ 202	$ 303
Due after one year through five years, amortized cost	1,351	1,229
Due after five years through 10 years, amortized cost	115	100
Total, amortized cost	1,668	1,632
Due within one year, fair value	203	305
Due after one year through five years, fair value	1,358	1,236
Due after five years through 10 years, fair value	116	101
Total, fair value	$ 1,677	$ 1,642