Loans and Leases and the Allowance for Credit Losses - Outstanding Principal Balance and Carrying Amount of Loans that is Included in Consolidated Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Outstanding principal and carrying value of acquired loans recorded at fair value
Outstanding principal balance	$ 4,302,336	$ 4,656,811
Carrying amount	3,697,582	4,007,452
Commercial, Financial, Leasing, etc. [Member]
Outstanding principal and carrying value of acquired loans recorded at fair value
Carrying amount	474,612	580,685
Real Estate Commercial [Member]
Outstanding principal and carrying value of acquired loans recorded at fair value
Carrying amount	1,412,397	1,541,368
Residential Real Estate [Member]
Outstanding principal and carrying value of acquired loans recorded at fair value
Carrying amount	551,698	576,473
Consumer [Member]
Outstanding principal and carrying value of acquired loans recorded at fair value
Carrying amount	$ 1,258,875	$ 1,308,926