Loans and Leases - Summary of Commercial Loans and Leases by Credit Quality (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	$ 14,563,128	$ 12,190,440
Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	5,355,625	4,109,056
Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	3,079,605	2,601,722
Commercial Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	200,350	204,553
Total Commercial Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	8,635,580	6,915,331
Originated Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	11,770,152	11,031,979
Originated Loans and Leases [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	3,789,036	3,531,146
Originated Loans and Leases [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	2,643,116	2,534,351
Originated Loans and Leases [Member] | Commercial Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	200,350	204,553
Originated Loans and Leases [Member] | Total Commercial Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	6,632,502	6,270,050
Acquired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	2,792,976	1,158,461
Acquired Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	1,566,589	577,910
Acquired Loans [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	436,489	67,371
Acquired Loans [Member] | Total Commercial Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	2,003,078	645,281
Pass [Member] | Originated Loans and Leases [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	3,612,375	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	2,387,112	2,335,103
Pass [Member] | Originated Loans and Leases [Member] | Commercial Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	194,408	198,207
Pass [Member] | Originated Loans and Leases [Member] | Total Commercial Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	6,193,895	5,949,837
Pass [Member] | Acquired Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	1,301,203	464,162
Pass [Member] | Acquired Loans [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	371,294	56,446
Pass [Member] | Acquired Loans [Member] | Total Commercial Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	1,672,497	520,608
Special Mention [Member] | Originated Loans and Leases [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	106,555	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	89,891	109,539
Special Mention [Member] | Originated Loans and Leases [Member] | Commercial Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	2,107	2,447
Special Mention [Member] | Originated Loans and Leases [Member] | Total Commercial Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	198,553	164,873
Special Mention [Member] | Acquired Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	131,051	47,619
Special Mention [Member] | Acquired Loans [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	21,805	3,182
Special Mention [Member] | Acquired Loans [Member] | Total Commercial Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	152,856	50,801
Substandard [Member] | Originated Loans and Leases [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	69,872	61,411
Substandard [Member] | Originated Loans and Leases [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	159,497	87,380
Substandard [Member] | Originated Loans and Leases [Member] | Commercial Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	3,835	3,899
Substandard [Member] | Originated Loans and Leases [Member] | Total Commercial Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	233,204	152,690
Substandard [Member] | Acquired Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	132,639	66,129
Substandard [Member] | Acquired Loans [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	42,874	7,743
Substandard [Member] | Acquired Loans [Member] | Total Commercial Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	175,513	73,872
Doubtful [Member] | Originated Loans and Leases [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	234	321
Doubtful [Member] | Originated Loans and Leases [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	6,616	2,329
Doubtful [Member] | Originated Loans and Leases [Member] | Total Commercial Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	6,850	$ 2,650
Doubtful [Member] | Acquired Loans [Member] | Commercial Real Estate [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	1,696
Doubtful [Member] | Acquired Loans [Member] | Commercial and Industrial [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	516
Doubtful [Member] | Acquired Loans [Member] | Total Commercial Loans and Leases [Member]
Financing Receivable, Recorded Investment [Line Items]
Total commercial loans and leases	$ 2,212