Derivatives (Offsetting Derivative Assets and Liabilities Subject to Master Netting Arrangements) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Derivatives [Abstract]
Gross Amounts Recognized, Derivative Assets	$ 7,155	$ 4,788
Gross Amounts Offset in the Statement of Financial Position, Derivative Assets	(5,007)
Net Amounts Presented in the Statement of Financial Position, Derivative Assets	2,148	4,788
Gross Amounts Not Offset in the Statement of Financial Position - Financial Instruments, Derivative Assets	2,148	4,788
Gross Amounts Not offset in the Statement of Financial Position - Cash Collateral, Derivative Assets
Net Amounts Presented in the Statement of Financial Position, Derivative Assets
Gross Amounts Recognized, Derivative Liabilities	24,015	26,846
Gross Amounts Offset in the Statement of Financial Position, Derivative Liabilities	(20,077)
Net Amounts Presented in the Statement of Financial Position, Derivative Liabilities	3,938	26,846
Gross Amounts Not Offset in the Statement of Financial Position - Financial Instruments, Derivative Liabilities	2,148	4,788
Gross Amounts Not offset in the Statement of Financial Position -Cash Collateral, Derivative Liabilities	4,099	19,095
Net Amounts Presented in the Statement of Financial Position, Derivative Liabilities		$ 2,963
Net Amount, Derivative Liabilities	$ (2,309)