Securities - Summary of Securities Held for Investment and Securities Available for Sale (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
Marketable Securities [Abstract]
Held for investment, at cost (fair value: $11,351)	$ 11,269
Available for sale, at fair value	575,749
Total	$ 587,018	$ 527,627	$ 565,490

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

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