Components of Other Intangible Assets Subject to Amortization (Detail) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010
Finite-Lived Intangible Assets [Line Items]
Gross Amount	$ 85,872	$ 85,872	$ 89,459
Accumulated Amortization	37,800	33,290	32,087
Core deposit intangible
Finite-Lived Intangible Assets [Line Items]
Gross Amount	80,591	80,591	80,591
Accumulated Amortization	34,008	29,817	25,625
Other customer relationships
Finite-Lived Intangible Assets [Line Items]
Gross Amount	5,092	5,092	8,743
Accumulated Amortization	3,726	3,430	6,372
Other intangibles
Finite-Lived Intangible Assets [Line Items]
Gross Amount	189	189	125
Accumulated Amortization	$ 66	$ 43	$ 90