Investment Securities - Narrative (Details) $ in Millions	9 Months Ended
Sep. 30, 2019 USD ($) security	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Investments, Debt and Equity Securities [Abstract]
Pledged securities not separately reported	$ 45,680		$ 38,870
Losses from other-than-temporary impairment	1	$ 2
Gross pre-tax unrealized losses	$ 104
Number of securities in loss position \| security	487

Disclosure regarding factors used to determine that the impairment of securities categorized as held-to-maturity or available-for-sale where cost exceeds fair value is not an other than temporary impairment (OTTI). This item contains disclosure of the number of investment positions in the held-to-maturity and available-for-sale investments determined to be temporarily impaired.

No definition available.

+ Details

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- Definition

The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 8A
-URI http://asc.fasb.org/extlink&oid=118954083&loc=SL6284422-111562

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- References

No definition available.

+ Details

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- Definition

Amount of unrealized gain (loss) on investment in marketable security, excluding other-than-temporary impairment (OTTI).

+ References

No definition available.

+ Details

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- Definition

Sum of the carrying amounts as of the date of the latest financial statement presented of securities which are owned but transferred to another party to serve as collateral to partially or fully secure a debt obligation, repurchase agreement or other current or potential obligation, and for which the transferee is not permitted to sell or re-pledge them to an unrelated party.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(i)
-URI http://asc.fasb.org/extlink&oid=109249958&loc=SL6224234-111729

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