Loans and Leases - Summary of Outstanding Principal Balance and Carrying Amount of Acquired Loans (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount	$ 14,563,128	$ 12,190,440
Accounted for under ASC 310-30 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding balance	2,730,575	1,258,418
Carrying amount	2,419,551	1,011,139
Accounted for under ASC 310-20 [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding balance	398,107	146,161
Carrying amount	367,775	140,595
Acquired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding balance	3,128,682	1,404,579
Carrying amount	$ 2,787,326	$ 1,151,734