Balance Sheet Offsetting - Financial Instruments Derivative Assets Liabilities and Resell Agreements Net of Amount Not Offset (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	$ 11,111	$ 5,266
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(11,111)	(5,236)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets	0	0
Net Amount, Derivatives, Financial Assets	0	30
Net Amount Recognized, Resell Agreements, Financial Assets	0	31,299
Gross Amounts Not Offset, Financial Instruments, Resell Agreements, Financial Assets	0	0
Gross Amounts Not Offset, Collateral, Resell Agreements, Financial Assets	0	(31,299)
Net Amount, Resell Agreements, Financial Assets	0	0
Net Amount Recognized, Total Financial Assets	11,111	36,565
Gross Amounts Not Offset, Collateral, Financial Assets	0	(31,299)
Net Amount, Financial Assets	0	30
Net Amount Recognized, Derivatives, Financial Liabilities	69,323	26,640
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities	(11,111)	(5,236)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities	(57,031)	(21,404)
Net Amount, Derivatives, Financial Liabilities	1,181	0
Net Amount Recognized, Repurchase Agreements, Financial Liabilities	2,068,147	1,668,142
Gross Amounts Not Offset, Financial Instruments, Repurchase Agreements, Financial Liabilities	0	0
Gross Amounts Not Offset, Collateral, Repurchase Agreements, Financial Liabilities	(2,068,147)	(1,668,142)
Net Amount, Repurchase Agreements, Financial Liabilities	0	0
Net Amount Recognized, Financial Liabilities	2,137,470	1,694,782
Gross Amounts Not Offset, Collateral, Financial Liabilities	(2,125,178)	(1,689,546)
Net Amount, Financial Liabilities	1,181	0
Counterparty A [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	2	39
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(2)	(39)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets	0	0
Net Amount, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivatives, Financial Liabilities	6,430	5,192
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities	(2)	(39)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities	(6,428)	(5,153)
Net Amount, Derivatives, Financial Liabilities	0	0
Counterparty B [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	5,838	1,650
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(5,838)	(1,650)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets	0	0
Net Amount, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivatives, Financial Liabilities	20,722	7,424
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities	(5,838)	(1,650)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities	(14,700)	(5,774)
Net Amount, Derivatives, Financial Liabilities	184	0
Counterparty C [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	0	1
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	0	(1)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets	0	0
Net Amount, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivatives, Financial Liabilities	71	135
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities	0	(1)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities	(71)	(134)
Net Amount, Derivatives, Financial Liabilities	0	0
Other Counterparties [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	5,271	3,576
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(5,271)	(3,546)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets	0	0
Net Amount, Derivatives, Financial Assets	0	30
Net Amount Recognized, Derivatives, Financial Liabilities	42,100	13,889
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities	(5,271)	(3,546)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities	(35,832)	(10,343)
Net Amount, Derivatives, Financial Liabilities	$ 997	$ 0