Balance Sheet Offsetting - Financial Instruments Derivative Assets Liabilities and Resell Agreements Net of Amount Not Offset (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	$ 5,266	$ 27,849
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(5,236)	(6,143)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets	0	(21,651)
Net Amount, Derivatives, Financial Assets	30	55
Net Amount Recognized, Resell Agreements, Financial Assets	31,299	11,642
Gross Amounts Not Offset, Financial Instruments, Resell Agreements, Financial Assets	0	0
Gross Amounts Not Offset, Collateral, Resell Agreements, Financial Assets	(31,299)	(11,642)
Net Amount, Resell Agreements, Financial Assets	0	0
Net Amount Recognized, Total Financial Assets	36,565	39,491
Gross Amounts Not Offset, Collateral, Financial Assets	(31,299)	(33,293)
Net Amount, Financial Assets	30	55
Net Amount Recognized, Derivatives, Financial Liabilities	26,640	11,185
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities	(5,236)	(6,143)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities	(21,404)	(4,621)
Net Amount, Derivatives, Financial Liabilities	0	421
Net Amount Recognized, Repurchase Agreements, Financial Liabilities	1,668,142	1,360,298
Gross Amounts Not Offset, Financial Instruments, Repurchase Agreements, Financial Liabilities	0	0
Gross Amounts Not Offset, Collateral, Repurchase Agreements, Financial Liabilities	(1,668,142)	(1,360,298)
Net Amount, Repurchase Agreements, Financial Liabilities	0	0
Net Amount Recognized, Financial Liabilities	1,694,782	1,371,483
Gross Amounts Not Offset, Collateral, Financial Liabilities	(1,689,546)	(1,364,919)
Net Amount, Financial Liabilities	0	421
Counterparty A [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	39	598
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(39)	(598)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets	0	0
Net Amount, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivatives, Financial Liabilities	5,192	4,293
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities	(39)	(598)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities	(5,153)	(3,651)
Net Amount, Derivatives, Financial Liabilities	0	44
Counterparty B [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	1,650	7,255
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(1,650)	(3,380)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets	0	(3,875)
Net Amount, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivatives, Financial Liabilities	7,424	3,380
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities	(1,650)	(3,380)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities	(5,774)	0
Net Amount, Derivatives, Financial Liabilities	0	0
Counterparty C [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Net Amount Recognized, Derivatives, Financial Assets	1	81
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(1)	(81)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets	0	0
Net Amount, Derivatives, Financial Assets	0	0
Net Amount Recognized, Derivatives, Financial Liabilities	135	326
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities	(1)	(81)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities	(134)	(245)
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	3,576	19,915
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Assets	(3,546)	(2,084)
Gross Amounts Not Offset, Collateral, Derivatives, Financial Assets	0	(17,776)
Net Amount, Derivatives, Financial Assets	30	55
Net Amount Recognized, Derivatives, Financial Liabilities	13,889	3,186
Gross Amounts Not Offset, Financial Instruments, Total Derivatives, Financial Liabilities	(3,546)	(2,084)
Gross Amounts Not offset, Collateral, Derivatives, Financial Liabilities	(10,343)	(725)
Net Amount, Derivatives, Financial Liabilities	$ 0	$ 377