Short-Term and Long-Term Debt Short-Term Debt (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Short-Term Debt [Line Items]
Federal Funds Purchased and Securities Sold under Agreements to Repurchase	$ 131	$ 0
Federal Funds Purchased and Securities Sold under Agreements to Repurchase [Member]
Short-Term Debt [Line Items]
Debt, Weighted Average Interest Rate	2.25%	0.00%
Intraday line of credit [Member]
Short-Term Debt [Line Items]
Line of credit maximum borrowing capacity	$ 15,000	$ 15,000
Fannie Mae [Member]
Short-Term Debt [Line Items]
Short-term debt, outstanding	$ 22,901	$ 24,896
Short-term debt, weighted-average interest rate	2.39%	2.29%

Weighted average interest rate of debt outstanding.

No definition available.

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- Definition

Amount after offset of short term borrowing where a bank borrows, at the federal funds rate, from another bank and securities that an entity sells and agrees to repurchase at a specified date for a specified price.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.13(1))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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- Definition

Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19)(a))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16)(a)(1))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(13))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Weighted average interest rate of short-term debt outstanding calculated at point in time.

+ References

+ Details

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- Details

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- Details

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- Details

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