Borrowings (Short-Term Borrowings) (Details) - Federal Funds Purchased And Repurchase Agreements [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Short-term Debt [Line Items]
Year End Weighted Rate	0.90%	0.80%	0.40%
Average Weighted Rate	1.30%	0.70%	0.30%
Average Balance Outstanding	$ 1,514,144	$ 1,462,387	$ 1,266,093
Maximum Outstanding at any Month End	1,981,761	1,984,071	1,723,905
Balance at December 31	$ 1,956,389	$ 1,507,138	$ 1,723,905