Goodwill and Other Intangible Assets - Components of Other Intangible Assets and Related Amortization (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Finite-Lived Intangible Assets [Line Items]
Purchase Value	$ 247,500	$ 243,022
Accumulated Amortization	58,091	31,947
Carrying Value	189,409	211,075
Aggregate amortization expense	32,067	16,551	2,728
Core deposit intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Purchase Value	200,547	206,047
Accumulated Amortization	45,832	27,691
Carrying Value	154,715	178,356
Aggregate amortization expense	23,642	14,474	2,491
Credit card and trust relationships [Member]
Finite-Lived Intangible Assets [Line Items]
Purchase Value	22,400	22,400
Accumulated Amortization	4,980	1,908
Carrying Value	17,420	20,492
Aggregate amortization expense	3,072	1,908
Value of insurance business acquired [Member]
Finite-Lived Intangible Assets [Line Items]
Purchase Value	2,431	2,431
Accumulated Amortization	2,084	1,926
Carrying Value	347	505
Aggregate amortization expense	158	169	213
Non-compete agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Purchase Value	400	322
Accumulated Amortization	100	322
Carrying Value	300
Aggregate amortization expense	100		14
Trade name [Member]
Finite-Lived Intangible Assets [Line Items]
Purchase Value	11,722	11,822
Accumulated Amortization	4,124	100
Carrying Value	7,598	11,722
Aggregate amortization expense	4,124		10
Merchant Processing Relationships[Member]
Finite-Lived Intangible Assets [Line Items]
Purchase Value	10,000
Accumulated Amortization	971
Carrying Value	9,029
Aggregate amortization expense	$ 971