Derivative Instruments and Balance Sheet Offsetting (Balance Sheet Offsetting) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Offsetting derivative assets
Gross amounts recognized	$ 38,595	$ 18,681
Net amounts presented in the statements of financial position	38,595	18,681
Offsetting derivative liabilities
Gross amounts recognized	32,379	12,357
Net amounts presented in the statements of financial position	32,379	12,357
Interest rate swaps and customer-initiated derivatives
Offsetting derivative assets
Gross amounts recognized	36,791	15,228
Gross amounts offset in the statements of financial condition	0	0
Net amounts presented in the statements of financial position	36,791	15,228
Gross amounts of assets not offset in the statement of financial position
Financial instruments	0	0
Collateral (received)/posted	(16,120)	0
Net Amount	20,671	15,228
Offsetting derivative liabilities
Gross amounts recognized	30,822	10,139
Gross amounts offset in the statements of financial condition	0	0
Net amounts presented in the statements of financial position	30,822	10,139
Gross amounts of liabilities not offset in the statement of financial position
Financial instruments	0	0
Collateral (received)/posted	430	1,081
Net Amount	$ 30,392	$ 9,058