Goodwill and Other Intangible Assets (Detail) - Core Deposit Intangibles (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Finite-lived Intangible Assets [Roll Forward]
Balance at the beginning of the year	$ 33,775	$ 34,318	$ 42,832
Balance at the beginning of the year	18,193	16,145	22,276
Balance at the beginning of the year	15,582	18,173	20,556
Additions		781	1,419
Amortization expense	(3,278)	(3,372)	(3,802)
Fully amortized assets	0	(1,324)	(9,933)
Fully amortized assets	0	(1,324)	(9,933)
Balance at the end of the year	33,775	33,775	34,318
Balance at the end of the year	21,471	18,193	16,145
Balance at the end of the year	$ 12,304	$ 15,582	$ 18,173
Weighted-average remaining life (in years)	5 years 11 months	6 years 5 months	6 years 11 months
Minimum
Finite-lived Intangible Assets [Roll Forward]
Estimated useful lives (in years)	3 years 3 months 18 days	3 years 3 months 18 days	3 years 3 months 18 days
Maximum
Finite-lived Intangible Assets [Roll Forward]
Estimated useful lives (in years)	12 years 9 months 18 days	12 years 9 months 18 days	12 years 7 months 6 days