Borrowings - Stated Maturity and Maturity to Call Date (Details) $ in Thousands	Dec. 31, 2020 USD ($)
Debt Instrument [Line Items]
Stated maturity, 2021	$ 4,303,796
Stated maturity, 2022	3,686,363
Stated maturity, 2023	2,141,735
Stated maturity, 2024	1,095,955
Stated maturity, 2025	1,358,075
Stated maturity, 2026 and after	1,752,977
Maturity to call date, 2021	4,303,796
Maturity to Call Date, 2022	3,686,363
Maturity to Call Date, 2023	2,141,735
Maturity to Call Date, 2024	1,095,955
Maturity to Call Date, 2025	1,358,075
Maturity to Call Date, 2026 and after	1,752,977
Total principal amount, maturity to call date	14,338,901
Hedge accounting adjustments	108,913
Total principal amount, after adjustments	14,447,814
Brokered Deposits
Debt Instrument [Line Items]
Stated maturity, 2021	3,691,601
Stated maturity, 2022	2,918,823
Stated maturity, 2023	1,536,077
Stated maturity, 2024	499,112
Stated maturity, 2025	270,274
Stated maturity, 2026 and after	47,401
Maturity to call date, 2021	3,691,601
Maturity to Call Date, 2022	2,918,823
Maturity to Call Date, 2023	1,536,077
Maturity to Call Date, 2024	499,112
Maturity to Call Date, 2025	270,274
Maturity to Call Date, 2026 and after	47,401
Total principal amount, maturity to call date	8,963,288
Hedge accounting adjustments	108,913
Total principal amount, after adjustments	9,072,201
Unsecured Debt
Debt Instrument [Line Items]
Stated maturity, 2021	0
Stated maturity, 2022	200,000
Stated maturity, 2023	0
Stated maturity, 2024	0
Stated maturity, 2025	500,000
Stated maturity, 2026 and after	0
Maturity to call date, 2021	0
Maturity to Call Date, 2022	200,000
Maturity to Call Date, 2023	0
Maturity to Call Date, 2024	0
Maturity to Call Date, 2025	500,000
Maturity to Call Date, 2026 and after	0
Total principal amount, maturity to call date	700,000
Hedge accounting adjustments	0
Total principal amount, after adjustments	700,000
Secured Borrowings
Debt Instrument [Line Items]
Stated maturity, 2021	612,195
Stated maturity, 2022	567,540
Stated maturity, 2023	605,658
Stated maturity, 2024	596,843
Stated maturity, 2025	587,801
Stated maturity, 2026 and after	1,705,576
Maturity to call date, 2021	612,195
Maturity to Call Date, 2022	567,540
Maturity to Call Date, 2023	605,658
Maturity to Call Date, 2024	596,843
Maturity to Call Date, 2025	587,801
Maturity to Call Date, 2026 and after	1,705,576
Total principal amount, maturity to call date	4,675,613
Hedge accounting adjustments	0
Total principal amount, after adjustments	$ 4,675,613

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04.(a))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e24072-122690

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601

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