Loans (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended						3 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012		Sep. 30, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Gains Losses	$ 3,771	[1]	$ 4,717	[1]	$ 7,422	[1]
Carrying Amount of Loans Sold	166,109		150,248		226,490
Loans held-for-sale	3,450	[2]	1,560	[2]	82,647	[2]
Provision for loan and covered loan losses	19,168		16,257		158,052
Bulk Sales Of Loan Pools
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Gains Losses					5,153	[1]
Carrying Amount of Loans Sold					169,577
Loans held-for-sale					80,260	[2]	80,300
Provision for loan and covered loan losses							62,300
Mortgage Loan Sales
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Gains Losses	3,771	[1]	4,717	[1]	2,269	[1]
Carrying Amount of Loans Sold	144,909		147,413		50,326
Loans held-for-sale	$ 0	[2]	$ 0	[2]	$ 0	[2]

[1] The net gains on the bulk loan sales represent gains realized subsequent to the transfer to held-for-sale and are included as a separate component of noninterest income in the Consolidated Statements of Income. Net gains on mortgage loan sales are included in mortgage banking income in the Consolidated Statements of Income.

[2] Amount represents charge-offs to the allowance for loan and covered loan losses at the time the loans were identified for sale