Loans and Leases - Summary of Commercial Loans and Leases by Credit Quality (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Originated Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	$ 6,382,227	$ 6,270,050
Originated Loans and Leases [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	3,605,301	3,531,146
Originated Loans and Leases [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	2,574,321	2,534,351
Originated Loans and Leases [Member] | Commercial Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	202,605	204,553
Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	2,120,305	645,281
Acquired Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	1,648,359	577,910
Acquired Loans [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	471,946	67,371
Pass [Member] | Originated Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	5,986,977	5,949,837
Pass [Member] | Originated Loans and Leases [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	3,445,547	3,416,527
Pass [Member] | Originated Loans and Leases [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	2,346,483	2,335,103
Pass [Member] | Originated Loans and Leases [Member] | Commercial Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	194,947	198,207
Pass [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	1,701,041	520,608
Pass [Member] | Acquired Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	1,331,863	464,162
Pass [Member] | Acquired Loans [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	369,178	56,446
Special Mention [Member] | Originated Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	214,955	164,873
Special Mention [Member] | Originated Loans and Leases [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	97,426	52,887
Special Mention [Member] | Originated Loans and Leases [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	114,408	109,539
Special Mention [Member] | Originated Loans and Leases [Member] | Commercial Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	3,121	2,447
Special Mention [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	179,923	50,801
Special Mention [Member] | Acquired Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	156,709	47,619
Special Mention [Member] | Acquired Loans [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	23,214	3,182
Substandard [Member] | Originated Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	174,283	152,690
Substandard [Member] | Originated Loans and Leases [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	61,928	61,411
Substandard [Member] | Originated Loans and Leases [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	107,818	87,380
Substandard [Member] | Originated Loans and Leases [Member] | Commercial Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	4,537	3,899
Substandard [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	230,826	73,872
Substandard [Member] | Acquired Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	152,929	66,129
Substandard [Member] | Acquired Loans [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	77,897	7,743
Doubtful [Member] | Originated Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	6,012	2,650
Doubtful [Member] | Originated Loans and Leases [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	400	321
Doubtful [Member] | Originated Loans and Leases [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	5,612	$ 2,329
Doubtful [Member] | Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	8,515
Doubtful [Member] | Acquired Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	6,858
Doubtful [Member] | Acquired Loans [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	$ 1,657