Covered Loans - Schedule of Acquired Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Impaired Loans By Type [Line Items]
Beginning Balance	$ 247,752	$ 456,788
Principal reductions and interest payments	(78,174)	(116,204)
Accretion of loan discount	19,174	26,102
Changes in contractual and expected cash flows due to remeasurement	134	(5,317)
Removals due to foreclosure or sale	(8,479)	(6,752)
Ending Balance	180,407	354,617
Contractual [Member]
Impaired Loans By Type [Line Items]
Beginning Balance	424,527	729,496
Principal reductions and interest payments	(78,174)	(116,204)
Changes in contractual and expected cash flows due to remeasurement	(14,514)	13,829
Removals due to foreclosure or sale	(7,764)	(17,030)
Ending Balance	324,075	610,091
Non Accretable Difference [Member]
Impaired Loans By Type [Line Items]
Beginning Balance	(90,996)	(180,655)
Changes in contractual and expected cash flows due to remeasurement	23,521	16,532
Removals due to foreclosure or sale	948	8,952
Ending Balance	(66,527)	(155,171)
Accretable Yield [Member]
Impaired Loans By Type [Line Items]
Beginning Balance	(85,779)	(92,053)
Accretion of loan discount	19,174	26,102
Changes in contractual and expected cash flows due to remeasurement	(8,873)	(35,678)
Removals due to foreclosure or sale	(1,663)	1,326
Ending Balance	$ (77,141)	$ (100,303)