Fair Value of Assets & Liabilities - Summary Of Changes In Level 3 Assets And Liabilities Measured At Fair Value (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	$ (26,545)	$ (9,425)	$ (31,540)	$ (5,645)
Net income	(4,008)	(529)	(3,892)	(4,904)
Purchases	0	(28,100)	0	(28,100)
Sales	0	0	0	0
Settlements	2,468	3,842	7,347	4,437
Net transfers into/(out of) Level 3	0	0	0	0
Ending balance	(28,085)	(34,212)	(28,085)	(34,212)
Net unrealized gains/(losses) included in net income	(4,008)	(530)	(3,892)	(4,904)
Trading securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	1,255	1,724	1,524	2,151
Net income	(157)	33	(128)	173
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements	0	(165)	(298)	(732)
Net transfers into/(out of) Level 3	0	0	0	0
Ending balance	1,098	1,592	1,098	1,592
Net unrealized gains/(losses) included in net income	0	(3)	(66)	59
Interest- only strips- AFS
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	17,792	5,787	9,902	1,270
Net income	(1,421)	(456)	(2,820)	840
Purchases	0	0	86	0
Sales	(11,401)	(2,034)	(38,612)	(11,227)
Settlements	0	0	0	0
Net transfers into/(out of) Level 3	10,279	7,064	46,693	19,478
Ending balance	15,249	10,361	15,249	10,361
Net unrealized gains/(losses) included in net income	(1,977)	(215)	(1,250)	(279)
Loans held- for-sale
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	15,092	16,718	16,273	18,926
Net income	443	277	1,259	986
Purchases	0	0	10	62
Sales	0	0	0	0
Settlements	(1,126)	(759)	(3,133)	(3,382)
Net transfers into/(out of) Level 3	0	0	0	(356)
Ending balance	14,409	16,236	14,409	16,236
Net unrealized gains/(losses) included in net income	$ 443	$ 277	$ 1,259	$ 986

Amount of unrealized gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3) and still held.

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Amount of transfer of financial instrument classified as an asset into (out of) level 3 of the fair value hierarchy.

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Amount of unrealized gain (loss) recognized in income for derivative asset (liability) after deduction of derivative liability (asset), measured at fair value using unobservable input (level 3) and still held.

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Amount of gain (loss) recognized in income from derivative asset (liability) after deduction of derivative liability (asset), measured at fair value on recurring basis using unobservable input (level 3).

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Amount of purchases of financial instrument classified as a derivative asset (liability) after deduction of derivative liability (asset), measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of sales of financial instrument classified as a derivative asset (liability) after deduction of derivative liability (asset), measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of transfers of financial instrument classified as a derivative asset (liability) after deduction of derivative liability (asset) into (out of) level 3 of the fair value hierarchy.

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