Derivatives (Offsetting of Derivatives) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Derivative Assets
Gross Amounts Recognized	$ 242,876	$ 107,816
Less: Master netting agreements	(40,372)	(31,569)
Less: Cash collateral received/pledged	(3,831)	(13,577)
Derivative asset, after netting	198,673	62,670
Less: Security Collateral Received	0	(13,975)
Net derivative assets	198,673	48,695
Derivative assets subject to master netting arrangements, gross amounts recognized	240,800	105,900
Contracts not subject to master netting arrangements, gross amounts recognized	2,100	2,000
Derivative, cash collateral received, including amount offset by fair value assets, and excess cash amount	4,600	15,800
Amount used to offset against derivative assets	3,831	13,577
Derivative Liabilities
Gross Amounts Recognized	172,923	118,305
Less: Master netting agreements	(40,372)	(31,569)
Less: Cash collateral received/pledged	(34,122)	(6,833)
Derivative liability, after netting	98,429	79,903
Less: Security Collateral Pledged	(76,434)	(11,231)
Net derivative liabilities	21,995	68,672
Derivative liability subject to master netting arrangements, gross amounts recognized	172,900	118,200
Contracts not subject to master netting arrangements, gross amounts recognized	17	102
Derivative, cash collateral posted against derivative liabilities, including amount offset the derivative fair value liabilities, and excess cash amount	36,400	8,400
Amount used to offset against derivative liabilities	$ 34,122	$ 6,833