Loans - Changes in Carrying Amount of Covered Acquired Loans and Accretable Yield for Loans Receivable (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Covered loans [Member]
Financing Receivable, Impaired [Line Items]
Carrying Amount of Loans, Balance at beginning of period	$ 671,443	$ 809,459
Carrying Amount of Loans, Payments received, net	(200,719)	(193,432)
Carrying Amount of Loans, Accretion	45,099	55,416
Carrying Amount of Loans, Balance at end of period	515,823	671,443
Accretable Discount, Balance at beginning of period	153,137	107,638
Accretable Discount, Accretion	(45,099)	(55,416)
Accretable Discount, Decrease in expected cash flows based on actual cash flow, loan sales and foreclosures assumptions	(19,326)	(18,930)
Accretable Discount, Net transfer from (to) nonaccretable difference to accretable yield	26,882	119,845
Accretable Discount, Balance at end of period	115,594	153,137
Non-Covered [Member]
Financing Receivable, Impaired [Line Items]
Carrying Amount of Loans, Balance at beginning of period	339,452
Carrying Amount of Loans, Additions		535,489
Carrying Amount of Loans, Payments received, net	(250,338)	(206,306)
Carrying Amount of Loans, Accretion	52,087	10,269
Carrying Amount of Loans, Balance at end of period	141,201	339,452
Accretable Discount, Balance at beginning of period	130,691
Accretable Discount, Additions		132,136
Accretable Discount, Accretion	(52,087)	(22,719)
Accretable Discount, Decrease in expected cash flows based on actual cash flow, loan sales and foreclosures assumptions	23,688	(26,630)
Accretable Discount, Net transfer from (to) nonaccretable difference to accretable yield	100,894	47,904
Accretable Discount, Balance at end of period	$ 203,186	$ 130,691