Refers to defined benefit plan liabilities for unsettled trades net.

No definition available.

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- References

No definition available.

+ Details

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- Definition

Refers to the percentage of mutual fund in investment in total fixed income investment grade.

+ References

No definition available.

+ Details

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- Definition

Refers to the percentage of pooled bond funds in total investment in fixed income investment grade.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	instant

- Definition

Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

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Pension and Other Postretirement Benefits, Fair Value of Postretirement Benefit Plans Assets (Details) - Postretirement Benefit Plans [Member] - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity securities [Abstract]
Fair value of company's plan assets	$ 67	$ 60	$ 57
Percentage of mutual fund in total investment in fixed income - investment grade securities	77.00%	73.00%
Percentage of pooled bond funds in total investment in fixed income - investment grade securities	23.00%	27.00%
Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	$ 53	$ 49
Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	11	8
Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	0	0
U.S. Equity [Member]
Equity securities [Abstract]
Fair value of company's plan assets	38	37
U.S. Equity [Member] \| Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	38	37
U.S. Equity [Member] \| Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	0	0
U.S. Equity [Member] \| Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	0	0
International Equity [Member]
Equity securities [Abstract]
Fair value of company's plan assets	2	1
International Equity [Member] \| Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	2	1
International Equity [Member] \| Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	0	0
International Equity [Member] \| Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	0	0
Fixed Income - Investment Grade [Member]
Equity securities [Abstract]
Fair value of company's plan assets	13	11
Fixed Income - Investment Grade [Member] \| Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	10	8
Fixed Income - Investment Grade [Member] \| Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	3	3
Fixed Income - Investment Grade [Member] \| Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	0	0
Fixed Income - High Yield [Member]
Equity securities [Abstract]
Fair value of company's plan assets	3	2
Fixed Income - High Yield [Member] \| Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	0	0
Fixed Income - High Yield [Member] \| Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	3	2
Fixed Income - High Yield [Member] \| Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	0	0
Real Estate Investment Trusts [Member]
Equity securities [Abstract]
Fair value of company's plan assets	3	3
Real Estate Investment Trusts [Member] \| Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	3	3
Real Estate Investment Trusts [Member] \| Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	0	0
Real Estate Investment Trusts [Member] \| Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	0	0
Other [Member]
Equity securities [Abstract]
Fair value of company's plan assets	5	3
Other [Member] \| Level 1 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	0	0
Other [Member] \| Level 2 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	5	3
Other [Member] \| Level 3 [Member]
Equity securities [Abstract]
Fair value of company's plan assets	0	0
Total Assets at Fair Value [Member]
Equity securities [Abstract]
Fair value of company's plan assets	64	57
Other Investments Measured at Net Asset Value [Member]
Equity securities [Abstract]
Liabilities for unsettled trades, net	$ 3	$ 3