Scheduled Maturities of Available-for-Sale Debt Securities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Due within one year, amortized cost	$ 658	$ 8,699
Due after one year through five years, amortized cost	1,415	3,853
Due after five years through 10 years, amortized cost	347
Total, amortized cost	2,420	12,552
Due within one year, fair value	659	8,703
Due after one year through five years, fair value	1,437	3,856
Due after five years through 10 years, fair value	346
Total, fair value	$ 2,442	$ 12,559