Parent Company Financial Information (Condensed Balance Sheets) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets
Cash and due from banks	$ 260,180	$ 244,615
Interest-earning deposits	17,407	97,918
Total cash and cash equivalents	277,587	342,533	$ 224,238	$ 175,302
Goodwill	765,842	765,842	382,762	382,762
Other assets	280,250	284,621
Total Assets	13,095,145	12,716,886
Subordinated Debt	35,462	35,647
Junior Subordinated Notes	0	8,248
Liabilities and Shareholders’ Equity
Other liabilities	107,291	100,346
Total liabilities	11,061,496	10,766,964
Shareholders’ equity	2,033,649	1,949,922	1,251,012	1,242,128
Total liabilities and shareholders' equity	13,095,145	12,716,886
Parent Company [Member]
Assets
Cash and due from banks	945	533
Interest-earning deposits	7,226	8,765
Total cash and cash equivalents	8,171	9,298	$ 2,447	$ 3,989
Goodwill	4,729	4,729
Other assets	1,595	3,426
Total Assets	2,069,662	1,994,398
Subordinated Debt	35,462	35,647
Junior Subordinated Notes	0	8,248
Liabilities and Shareholders’ Equity
Other liabilities	551	581
Total liabilities	36,013	44,476
Shareholders’ equity	2,033,649	1,949,922
Total liabilities and shareholders' equity	2,069,662	1,994,398
Banking Subsidiaries [Member] | Parent Company [Member]
Assets
Investment in subsidiaries	2,049,855	1,971,788
Other Subsidiaries [Member] | Parent Company [Member]
Assets
Investment in subsidiaries	$ 5,312	$ 5,157