Loans and Allowance for Loan Losses - Changes in Carrying Amount of Covered Acquired Loans and Accretable Yield for Loans Receivable (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Covered loans [Member]
Financing Receivable, Impaired [Line Items]
Balance at beginning of period	$ 515,823	$ 671,443
Additions
Payments received, net	(150,405)	(200,719)
Accretion	26,584	45,099
Balance at end of period	392,002	515,823
Accretable Yield, Balance at beginning of period	115,594	153,137
Accretable Yield, Additions
Accretable Yield, Payments received, net	(861)
Accretable Yield, Accretion	(26,584)	(45,099)
Accretable Yield, Increase (decrease) in expected cash flows based on actual cash flow, loan sales and foreclosures assumptions	(12,944)	(19,326)
Accretable Yield, Net transfer from (to) nonaccretable difference to accretable yield	22,611	26,882
Accretable Yield, Balance at end of period	97,816	115,594
Non-Covered [Member]
Financing Receivable, Impaired [Line Items]
Balance at beginning of period	141,201	339,452
Additions
Payments received, net	(106,444)	(250,338)
Accretion	30,213	52,087
Balance at end of period	64,970	141,201
Accretable Yield, Balance at beginning of period	203,186	130,691
Accretable Yield, Additions
Accretable Yield, Payments received, net	(37,961)
Accretable Yield, Accretion	(30,213)	(52,087)
Accretable Yield, Increase (decrease) in expected cash flows based on actual cash flow, loan sales and foreclosures assumptions	6,465	23,688
Accretable Yield, Net transfer from (to) nonaccretable difference to accretable yield	5,636	100,894
Accretable Yield, Balance at end of period	$ 147,113	$ 203,186