Debt Securities According Contractual Terms (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014
Debt And Receivables Securitization [Line Items]
Amortized costs, In one year or less	$ 15,666
Amortized costs, After one year through five years	298,735
Amortized costs, After five years through ten years	184,351
Amortized costs, After ten years	27,663
Amortized costs, Total	526,415
Fair Values, In one year or less	15,771
Fair Values, After one year through five years	305,191
Fair Values, After five years through ten years	187,722
Fair Values, After ten years	28,583
Debt securities, fair values total	$ 537,267