Derivatives (Offsetting of Derivatives) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Derivative Assets
Gross Amounts Recognized	$ 358,639	$ 107,816
Less: Master netting agreements	(62,741)	(31,569)
Less: Cash collateral received/pledged	(6,587)	(13,577)
Derivative asset, after netting	289,311	62,670
Less: Security Collateral Received	0	(13,975)
Net derivative assets	289,311	48,695
Derivative assets subject to master netting arrangements, gross amounts recognized	357,000	105,900
Contracts not subject to master netting arrangements, gross amounts recognized	1,600	2,000
Derivative, cash collateral received, including amount offset by fair value assets, and excess cash amount	7,200	15,800
Amount used to offset against derivative assets	6,587	13,577
Derivative Liabilities
Gross Amounts Recognized	263,734	118,305
Less: Master netting agreements	(62,741)	(31,569)
Less: Cash collateral received/pledged	(47,979)	(6,833)
Derivative liability, after netting	153,014	79,903
Less: Security Collateral Pledged	(113,365)	(11,231)
Net derivative liabilities	39,649	68,672
Derivative liability subject to master netting arrangements, gross amounts recognized	263,700	118,200
Contracts not subject to master netting arrangements, gross amounts recognized	67	102
Derivative, cash collateral posted against derivative liabilities, including amount offset the derivative fair value liabilities, and excess cash amount	50,900	8,400
Amount used to offset against derivative liabilities	$ 47,979	$ 6,833