Loans and Other Repossessed Assets Acquired (Detail) - Summaries of nonperforming assets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Nonaccrual loans	$ 44,910	$ 45,891
Loans 90+ days, still accruing	6	43
Restructured loans, still accruing	3,768	3,536
Nonperforming loans	48,684	49,470
Other repossessed assets acquired	16,310	18,338
Nonperforming assets	64,994	67,808
Acquired Non-Covered Loans [Member]
Nonperforming loans	235	328
Nonperforming assets	1,226	2,023
Acquired Covered Loans [Member]
Restructured loans, still accruing	0	0
Nonperforming loans	8,769	8,649
Nonperforming assets	18,446	18,256
Legacy Loans [Member]
Nonperforming loans	39,680	40,493
Nonperforming assets	$ 45,322	$ 47,529