Securities - Carrying Value of Held-to-Maturity Investment Securities (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2014	Dec. 31, 2013
Investments Debt And Equity Securities [Abstract]
Amortized cost	$ 508,990
Net loss on date of transfer from available-for-sale	(13,347)
Amortization of net loss	468
Carrying value	$ 496,111	$ 495,599

Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant