Activity in Allowance for Losses for Non-Covered Loans and Covered Loans (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually evaluated for impairment		$ 2,685
Allowance for Loan Losses, Collectively evaluated for impairment	140,689	138,263
Allowance for Loan Losses, Acquired loans with deteriorated credit quality	60,431	51,311
Allowance for Loan Losses	201,120	192,259
Mortgage Receivable
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually evaluated for impairment		1,486
Allowance for Loan Losses, Collectively evaluated for impairment	123,915	126,448
Allowance for Loan Losses, Acquired loans with deteriorated credit quality	39,086	32,593
Allowance for Loan Losses	163,001	160,527
Other loan
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Loan Losses, Individually evaluated for impairment		1,199
Allowance for Loan Losses, Collectively evaluated for impairment	16,774	11,815
Allowance for Loan Losses, Acquired loans with deteriorated credit quality	21,345	18,718
Allowance for Loan Losses	$ 38,119	$ 31,732