Parent Company Information - Schedule of Condensed Statements of Financial Condition (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Interest bearing deposits with banks	$ 170,225	$ 367,838
Investment securities available for sale	1,506,861	886,970
Other assets	655,814	551,876
Total Assets	21,612,616	18,792,491
Long-term borrowings	1,810,728	2,525,044
Junior subordinated debentures issued to capital trusts	41,414	41,252
Shareholders’ equity	2,207,091	1,863,017	$ 1,541,040	$ 1,502,377
Total Liabilities and Shareholders’ Equity	21,612,616	18,792,491
Parent Company [Member]
Cash	63,330	78,163
Interest bearing deposits with banks	135	135
Investment securities available for sale	806	833
Investments in and receivables due from subsidiaries	2,398,784	1,968,736
Other assets	61,365	16,771
Total Assets	2,524,420	2,064,638
Dividends payable to shareholders	28,054	25,512
Long-term borrowings	230,573	129,993
Junior subordinated debentures issued to capital trusts	41,414	41,252
Accrued expenses and other liabilities	17,288	4,864
Shareholders’ equity	2,207,091	1,863,017
Total Liabilities and Shareholders’ Equity	$ 2,524,420	$ 2,064,638