Loans and Leases (Outstanding Principal Balance and the Related Carrying Amount of Acquired Loans) (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Loans Individually Evaluated For Impairment [Member]
Acquired Loans Unpaid Principal Balance And Related Carrying Amount [Line Items]
Unpaid principal balance	$ 179,556	$ 238,538
Carrying amount	138,503	162,251
Loans Collectively Evaluated For Impairment [Member]
Acquired Loans Unpaid Principal Balance And Related Carrying Amount [Line Items]
Unpaid principal balance	1,619,425	1,976,132
Carrying amount	1,615,488	1,967,032
Purchased Loan [Member]
Acquired Loans Unpaid Principal Balance And Related Carrying Amount [Line Items]
Unpaid principal balance	1,798,981	2,214,670
Carrying amount	$ 1,753,991	$ 2,129,283