Derivatives (Offsetting of Derivatives) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Derivative Assets
Gross Amounts Recognized	$ 135,782	$ 107,816
Less: Master netting agreements	(39,118)	(31,569)
Less: Cash collateral received/pledged	(920)	(13,577)
Derivative asset, after netting	95,744	62,670
Less: Security Collateral Received	(1,097)	(13,975)
Net derivative assets	94,647	48,695
Derivative assets subject to master netting arrangements, gross amounts recognized	133,600	105,900
Contracts not subject to master netting arrangements, gross amounts recognized	2,200	2,000
Derivative, cash collateral received, including amount offset by fair value assets, and excess cash amount	920	15,800
Amount used to offset against derivative assets	920	13,577
Derivative Liabilities
Gross Amounts Recognized	109,587	118,305
Less: Master netting agreements	(39,118)	(31,569)
Less: Cash collateral received/pledged	(16,984)	(6,833)
Derivative liability, after netting	53,485	79,903
Less: Security Collateral Pledged	(26,191)	(11,231)
Net derivative liabilities	27,294	68,672
Derivative liability subject to master netting arrangements, gross amounts recognized	109,600	118,200
Contracts not subject to master netting arrangements, gross amounts recognized	9	102
Derivative, cash collateral posted against derivative liabilities, including amount offset the derivative fair value liabilities, and excess cash amount	20,000	8,400
Amount used to offset against derivative liabilities	$ 16,984	$ 6,833