Fair Value of Assets and Liabilities - Changes in Level 3 Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Fair Value, Mortgage Servicing Rights Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Fair Value, Mortgage Servicing Rights, Beginning Balance	$ 1,068	$ 1,212	$ 1,126	$ 1,290
Fair Value, Mortgage Servicing Rights, Realized and Unrealized Net Gains (Losses) Included in Net Income	(50)	(38)	(108)	(116)
Fair Value, Mortgage Servicing Rights, Ending Balance	1,018	1,174	1,018	1,174
Fair Value, Mortgage Service Rights, Total Unrealized Net Gains (Losses) Included in Net Income Related to Assets Still Held	0	0	0	0
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Fair Value, Net Derivative Assets and Liabilities, Beginning Balance	88,995	19,956	22,573	4,416
Fair Value, Net Derivative Assets and Liabilities, Realized and Unrealized Net Gains (Losses) Included in Net Income	4,909	4,360	15,372	9,602
Fair Value, Net Derivative Assets and Liabilities, Transfers to Loans Held for Sale	(4,242)	(3,736)	(13,521)	(7,750)
Variation margin payments for swap liabilities	(1,840)	11,331	63,398	25,643
Fair Value, Net Derivative Assets and Liabilities, Ending Balance	87,822	31,911	87,822	31,911
Fair Value, Net Derivative Assets and Liabilities,Total Unrealized Net Gains (Losses) Included in Net Income Related to Assets Still Held	$ 87,822	$ 31,911	$ 87,822	$ 31,911