Variable Interest Entities - Summary of Assets and Liabilities Related to Consolidated Variable Interest Entities (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Variable interest entities [Member]
Variable Interest Entity [Line Items]
Consolidated Assets	$ 146	$ 154
Consolidated Liabilities	132	132
Other assets [Member] \| Low income housing limited partnership investments [Member]
Variable Interest Entity [Line Items]
Consolidated Assets	146	154
Long-term debt [Member] \| Low income housing limited partnership investments [Member]
Variable Interest Entity [Line Items]
Consolidated Liabilities	73	73
Interest, taxes and other liabilities [Member] \| Low income housing limited partnership investments [Member]
Variable Interest Entity [Line Items]
Consolidated Liabilities	$ 59	$ 59

The carrying amount of the consolidated Variable Interest Entity's assets included in the reporting entity's statement of financial position.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (bb)
-URI http://asc.fasb.org/extlink&oid=77990344&loc=d3e5710-111685

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- Definition

The carrying amount of the consolidated Variable Interest Entity's liabilities included in the reporting entity's statement of financial position.

+ References

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- Definition

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+ References

No definition available.

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