Derivatives (Offsetting of Derivatives) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Derivative assets
Gross Amounts Recognized	$ 708,610	$ 330,316
Less: Master netting agreements	(104,456)	(121,561)
Less: Cash collateral received/pledged	(5,240)	(3,758)
Derivative asset, after netting	598,914	204,997
Less: Security Collateral Received	(8,647)	0
Net derivative assets	590,267	204,997
Derivative assets subject to master netting arrangements, gross amounts recognized	695,600	328,700
Contracts not subject to master netting arrangements, gross amounts recognized	13,000	1,600
Derivative, cash collateral received, including amount offset by fair value assets, and excess cash amount	9,100	3,800
Amount used to offset against derivative assets	5,240	3,758
Derivative liabilities
Gross Amounts Recognized	506,019	256,528
Less: Master netting agreements	(104,456)	(121,561)
Less: Cash collateral received/pledged	(97,675)	(38,238)
Derivative liability, after netting	303,888	96,729
Less: Security Collateral Pledged	(262,165)	(79,619)
Net derivative liabilities	41,723	17,110
Derivative liability subject to master netting arrangements, gross amounts recognized	505,800	256,500
Contracts not subject to master netting arrangements, gross amounts recognized	208	20
Derivative, cash collateral posted against derivative liabilities, including amount offset the derivative fair value liabilities, and excess cash amount	100,100	43,000
Amount used to offset against derivative liabilities	$ 97,675	$ 38,238