Derivatives (Offsetting Derivative Assets and Liabilities Subject to Master Netting Arrangements) (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivatives [Abstract]
Gross Amounts Recognized, Derivative Assets	$ 26,648	$ 7,155
Gross Amounts Offset in the Statement of Income, Derivative Assets	(19,897)	(5,007)
Net Amounts Presented in the Statement of Income, Derivative Assets	6,751	2,148
Gross Amounts Not Offset in the Statement of Income - Financial Instruments, Derivative Assets	309	2,148
Gross Amounts Not offset in the Statement of Income - Cash Collateral, Derivative Assets
Net Amounts Presented in the Statement of Income, Derivative Assets	6,442
Gross Amounts Recognized, Derivative Liabilities	26,437	24,015
Gross Amounts Offset in the Statement of Income, Derivative Liabilities	(26,128)	(20,077)
Net Amounts Presented in the Statement of Income, Derivative Liabilities	309	3,938
Gross Amounts Not Offset in the Statement of Income - Financial Instruments, Derivative Liabilities	309	2,148
Gross Amounts Not offset in the Statement of Income - Cash Collateral, Derivative Liabilities	2,263	4,099
Net Amounts Presented in the Statement of Income, Derivative Liabilities	$ (2,263)	$ (2,309)