Derivatives - Derivative Assets and Collateral Received (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Derivative [Line Items]
Gross amounts of recognized assets	$ 834,480	$ 182,984
Derivative liabilities available for offset	0	0
Net amount	834,480	182,984
Derivative liabilities available for offset	(27,506)	(18,896)
Collateral received	(385,723)	(145,334)
Net amount	421,251	18,754
Derivative assets not subject to master netting agreements	2,600	100
Derivatives, interest rate contracts
Derivative [Line Items]
Gross amounts of recognized assets	787,139	162,344
Derivative liabilities available for offset	0	0
Net amount	787,139	162,344
Derivative liabilities available for offset	(11,401)	(5,604)
Collateral received	(369,510)	(143,334)
Net amount	406,228	13,406
Forward Contracts
Derivative [Line Items]
Gross amounts of recognized assets	47,341	20,640
Derivative liabilities available for offset	0	0
Net amount	47,341	20,640
Derivative liabilities available for offset	(16,105)	(13,292)
Collateral received	(16,213)	(2,000)
Net amount	$ 15,023	$ 5,348