Derivative Instruments and Balance Sheet Offsetting - Balance Sheet Offsetting (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Offsetting derivative assets
Gross amounts recognized	$ 47,359	$ 38,595
Offsetting derivative liabilities
Gross amounts recognized	49,498	32,379
Interest rate swaps and customer-initiated derivatives
Offsetting derivative assets
Gross amounts recognized	44,672	36,791
Gross amounts offset in the statements of financial condition	0	0
Net amounts presented in the statements of financial position	44,672	36,791
Gross amounts not offset in the statements of financial position
Financial instruments	0	0
Collateral (received)/posted	(39,368)	(16,120)
Net Amount	5,304	20,671
Offsetting derivative liabilities
Gross amounts recognized	47,810	30,822
Gross amounts offset in the statements of financial condition	0	0
Net amounts presented in the statements of financial position	47,810	30,822
Gross amounts not offset in the statements of financial position
Financial instruments	0	0
Collateral (received)/posted	170	430
Net Amount	$ 47,640	$ 30,392