Impairment of Investment Securities - Cumulative Roll Forward of Credit Losses Recognized in Earnings for Debt Securities Held and Not Intended to be Sold (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014		Jun. 30, 2013
Impairment of Investment Securities Disclosure [Abstract]
Balance, beginning (a)	$ 27,254	$ 42,991	$ 27,543	[1]	$ 43,274	[1]
Credit losses on debt securities for which other-than-temporary impairment was not previously recognized	0	0	0		0
Additional credit losses on debt securities for which other-than-temporary impairment was previously recognized	0	0	0		0
Balance, ending	26,842	42,699	26,842		42,699
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Reductions, Cash Flows	$ (412)	$ (292)	$ (701)		$ (575)

[1] The beginning balance represents credit related losses included in other-than-temporary impairment charges recognized on debt securities in prior periods.