Fair Value of Financial Instruments (Detail) - Carrying value and fair value of the financial instruments (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Dec. 31, 2012		Mar. 31, 2012
Assets
Cash and cash equivalents	$ 129,300		$ 117,451		$ 63,524
Securities available for sale	314,597		253,798		442,531
Securities held to maturity	14,869		15,555		19,835
Nonmarketable securities	19,245		20,914		37,965
Total loans, net	2,428,715		2,451,145		2,304,791
Loans held for sale	33,752		55,201		52,339
FDIC indemnification asset	58,917		80,268		46,272
Other repossessed assets acquired1	16,310		18,338
Residential mortgage servicing rights1	774,550		782,672		719,923
Liabilities
Deposits	2,600,520		2,595,333		2,264,489
Advances from FHLB	233,000		233,000		533,000
Long-term debt	47,204		47,204		47,204
Carrying Value [Member]
Assets
Cash and cash equivalents	129,300		117,451
Securities available for sale	314,597		253,798
Securities held to maturity	14,869		15,555
Nonmarketable securities	19,245		20,914
Total loans, net	2,428,715		2,451,145
Loans held for sale	33,752		55,201
FDIC indemnification asset	58,917		80,268
Other repossessed assets acquired1	16,310	[1]	18,338	[1]
Residential mortgage servicing rights1	15,297	[1]	13,910	[1]
Accrued interest receivable1	8,675	[1]	8,564	[1]
Derivative financial instruments1	2,140	[1]	2,561	[1]
Liabilities
Deposits	2,600,520		2,595,333
Advances from FHLB	233,000		233,000
Long-term debt	47,204		47,204
FDIC true-up liability2	2,396	[2]	3,658	[2]
Accrued interest payable2	5,792	[2]	6,114	[2]
Fair Value [Member]
Assets
Cash and cash equivalents	129,300		117,451
Securities available for sale	314,597		253,798
Securities held to maturity	16,942		17,867
Nonmarketable securities	19,245		20,914
Total loans, net	2,471,335		2,502,376
Loans held for sale	33,752		55,201
FDIC indemnification asset	58,917		80,268
Other repossessed assets acquired1	16,310	[1]	18,338	[1]
Residential mortgage servicing rights1	15,297	[1]	13,910	[1]
Accrued interest receivable1	8,675	[1]	8,564	[1]
Derivative financial instruments1	2,140	[1]	2,561	[1]
Liabilities
Deposits	2,612,531		2,608,927
Advances from FHLB	258,517		260,409
Long-term debt	47,016		46,749
FDIC true-up liability2	2,396	[2]	3,658	[2]
Accrued interest payable2	$ 5,792	[2]	$ 6,114	[2]

[1] Included as part of other assets in the Consolidated Balance Sheets.

[2] Included as part of other liabilities in the Consolidated Balance Sheets.