Marketable Securities Scheduled Maturities of Available-for-Sale Debt Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Due within one year, amortized cost	$ 205	$ 303
Due after one year through five years, amortized cost	1,340	1,229
Due after five years through 10 years, amortized cost	111	100
Total, amortized cost	1,656	1,632
Due within one year, fair value	206	305
Due after one year through five years, fair value	1,347	1,236
Due after five years through 10 years, fair value	112	101
Total, fair value	$ 1,665	$ 1,642