Other Assets (Schedule of Other Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Accrued interest receivable	$ 64,044	$ 56,042
Derivative assets	32,256	47,501
Low-income housing tax credit investments	29,959	23,021
Prepaid expenses	21,047	19,013
Investment in unconsolidated trust subsidiaries	14,277	14,277
Income taxes receivable	13,360	4,841
Insurance premium receivable	9,555	7,557
Commercial servicing asset	5,169	6,391
Other	34,351	48,994
Total	$ 224,018	$ 227,637