Investments Gross Unrealized Losses and Fair Value, Aggregated by Investment Category and Length of Time, in Continuous Unrealized Loss Position (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Total, Fair Value	$ 34,600	$ 13,300
Collateralized mortgage obligations, Government sponsored agencies
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	12,849	4,962
Less than 12 months, Unrealized Losses	(94)	(10)
Total, Fair Value	12,849	5,076
Total, Unrealized Losses	(94)	(10)
Federal agencies
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	4,992	4,998
Less than 12 months, Unrealized Losses	(8)	(2)
Total, Fair Value	4,992	4,998
Total, Unrealized Losses	(8)	(2)
Municipals
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	878	874
Less than 12 months, Unrealized Losses	(13)	(16)
Total, Fair Value	878	874
Total, Unrealized Losses	(13)	(16)
Corporate obligations
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	13,397
Less than 12 months, Unrealized Losses	(24)
12 months or more, Fair Value	2,465	2,475
12 months or more, Unrealized Losses	(4,279)	(4,269)
Total, Fair Value	15,862	2,475
Total, Unrealized Losses	(4,303)	(4,269)
Total temporarily impaired securities
Schedule of Available-for-sale Securities [Line Items]
Less than 12 months, Fair Value	32,116	10,834
Less than 12 months, Unrealized Losses	(139)	(28)
12 months or more, Fair Value	2,465	2,475
12 months or more, Unrealized Losses	(4,279)	(4,269)
Total, Fair Value	34,581	13,309
Total, Unrealized Losses	$ (4,418)	$ (4,297)