Parent Company Information - Schedule of Condensed Statements of Financial Condition (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Condensed Balance Sheet Statements, Captions [Line Items]
Interest bearing deposits with banks	$ 171,710	$ 170,225
Investment securities available for sale	1,297,373	1,506,861
Other assets	583,654	656,999
Total Assets	22,864,439	21,612,616
Long-term borrowings	1,433,906	1,810,728
Junior subordinated debentures issued to capital trusts	41,577	41,414
Shareholders’ equity	2,377,156	2,207,091	$ 1,863,017	$ 1,541,040
Total Liabilities and Shareholders’ Equity	22,864,439	21,612,616
Parent Company
Condensed Balance Sheet Statements, Captions [Line Items]
Cash	68,927	63,330
Interest bearing deposits with banks	82	135
Investment securities available for sale	239	806
Investments in and receivables due from subsidiaries	2,591,982	2,398,784
Other assets	36,188	61,365
Total Assets	2,697,418	2,524,420
Dividends payable to shareholders	29,477	28,054
Long-term borrowings	236,731	230,573
Junior subordinated debentures issued to capital trusts	41,577	41,414
Accrued expenses and other liabilities	12,477	17,288
Shareholders’ equity	2,377,156	2,207,091
Total Liabilities and Shareholders’ Equity	$ 2,697,418	$ 2,524,420