Fair Value of Financial Instruments (Detail) - Financial Instruments Recorded at Fair Value on a Nonrecurring Basis (Fair Value, Measurements, Nonrecurring [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Assets
Loans held for sale	$ 33,752	$ 55,201
Impaired loans, net of specific allowance	33,502	24,632
Other repossessed assets acquired	16,310	18,338
Total	83,564	98,171
Fair Value, Inputs, Level 1 [Member]
Assets
Loans held for sale	0	0
Impaired loans, net of specific allowance	0	0
Other repossessed assets acquired	0	0
Total	0	0
Fair Value, Inputs, Level 2 [Member]
Assets
Loans held for sale	33,752	55,201
Impaired loans, net of specific allowance	0	0
Other repossessed assets acquired	0	0
Total	33,752	55,201
Fair Value, Inputs, Level 3 [Member]
Assets
Loans held for sale	0	0
Impaired loans, net of specific allowance	33,502	24,632
Other repossessed assets acquired	16,310	18,338
Total	49,812	42,970
Year to Date Losses [Member]
Assets
Loans held for sale	0	0
Impaired loans, net of specific allowance	3,752	3,511
Other repossessed assets acquired	408	1,138
Total	$ 4,160	$ 4,649