Summary of Other Noninterest Expense (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Other Income and Expenses [Abstract]
Telephone	$ 6,528		$ 5,835		$ 4,952
Client services	6,910		4,594		2,716
Data processing services	5,876		4,811		4,060
Tax credit fund amortization	3,911		4,474		3,965
Postage and supplies	2,482		2,162		2,198
Dues and publications	2,067		1,570		1,519
Net gain from note repurchases and termination of corresponding interest rate swaps	0	[1]	(3,123)	[1]	0	[1]
Other	8,188		10,499		7,081
Total other noninterest expense	$ 35,962		$ 30,822		$ 26,491

[1] Represents gains from the repurchase of 109 million of our 5.70% Senior Notes and $204 million of our 6.05% Subordinated Notes and the termination of the corresponding portions of interest rate swaps in 2011. For more information, see Note 11–"Short-Term Borrowings and Long-Term Debt."