Investments in Securities - Available-for-sale Securities 2 (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Consecutive Months, Gross Unrealized Losses in AOCI	$ (14)	$ (8)
Less than 12 Consecutive Months, Fair Value	167	228
12 Consecutive Months or Longer, Gross Unrealized Losses	(2)	(6)
12 Consecutive Months or Longer, Fair Value	36	102
Fannie Mae
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Consecutive Months, Gross Unrealized Losses in AOCI	(12)	(5)
Less than 12 Consecutive Months, Fair Value	158	225
12 Consecutive Months or Longer, Gross Unrealized Losses	(2)	(6)
12 Consecutive Months or Longer, Fair Value	36	102
Other securities
Debt Securities, Available-for-sale [Line Items]
Less Than 12 Consecutive Months, Gross Unrealized Losses in AOCI	(2)	(3)
Less than 12 Consecutive Months, Fair Value	9	3
12 Consecutive Months or Longer, Gross Unrealized Losses	0	0
12 Consecutive Months or Longer, Fair Value	$ 0	$ 0

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=124269663&loc=SL82922890-210455

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27337-111563

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 55
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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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-URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27337-111563

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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-Topic 326
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-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=124269663&loc=SL82922890-210455

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
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-Section 55
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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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