Fair Value of Financial Instruments (Detail) - Assets Not Recorded at Fair Value (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 held to maturity	16,942		17,867		22,553
Nonmarketable securities	19,245		20,914		37,965
Total loans, net	2,428,715		2,451,145		2,304,791
FDIC indemnification asset	58,917		80,268		46,272
Liabilities
Deposits	2,600,520		2,595,333		2,264,489
Advances from FHLB	233,000		233,000		533,000
Fair Value [Member] | Fair Value, Inputs, Level 1 [Member]
Assets
Cash and cash equivalents	129,300		117,451
Securities held to maturity	0		0
Nonmarketable securities	0		0
Total loans, net	0	[1]	0	[1]
FDIC indemnification asset	0		0
Accrued interest receivable2	8,675	[2]	8,564	[2]
Liabilities
Deposits	0		0
Advances from FHLB	0		0
Long term debt	0		0
FDIC true-up liability	2,396	[3]	3,658	[3]
Accrued interest payable	5,792	[3]	6,114	[3]
Fair Value [Member] | Fair Value, Inputs, Level 2 [Member]
Assets
Cash and cash equivalents	0		0
Securities held to maturity	16,942		17,867
Nonmarketable securities	0		0
Total loans, net	0	[1]	0	[1]
FDIC indemnification asset	0		0
Accrued interest receivable2	0	[2]	0	[2]
Liabilities
Deposits	0		0
Advances from FHLB	0		0
Long term debt	0		0
FDIC true-up liability	0	[3]	0	[3]
Accrued interest payable	0	[3]	0	[3]
Fair Value [Member] | Fair Value, Inputs, Level 3 [Member]
Assets
Cash and cash equivalents	0		0
Securities held to maturity	0		0
Nonmarketable securities	19,245		20,914
Total loans, net	2,437,833	[1]	2,477,744	[1]
FDIC indemnification asset	58,917		80,268
Accrued interest receivable2	0	[2]	0	[2]
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 liability	0	[3]	0	[3]
Accrued interest payable	0	[3]	0	[3]
Total Fair Value [Member]
Assets
Cash and cash equivalents	129,300		117,451
Securities held to maturity	16,942		17,867
Nonmarketable securities	19,245		20,914
Total loans, net	2,437,833	[1]	2,477,744	[1]
FDIC indemnification asset	58,917		80,268
Accrued interest receivable2	8,675	[2]	8,564	[2]
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 liability	2,396	[3]	3,658	[3]
Accrued interest payable	$ 5,792	[3]	$ 6,114	[3]

[1] Excludes impaired loans

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

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