Debt Securities According Contractual Terms (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013
Debt And Receivables Securitization [Line Items]
Amortized costs, In one year or less	$ 45,430
Amortized costs, After one year through five years	250,193
Amortized costs, After five years through ten years	193,574
Amortized costs, After ten years	22,194
Amortized costs, Total	511,391
Fair Values, In one year or less	45,467
Fair Values, After one year through five years	255,257
Fair Values, After five years through ten years	193,825
Fair Values, After ten years	22,099
Debt securities, fair values total	$ 516,648