Derivative Instruments - Schedule of Gross and Net Amount Offset (Details) - Balance Sheet Offsetting $ in Millions	Dec. 31, 2017 USD ($)
Change in unrealized gain (loss) on anticipated sales hedging:
Gross Fair Value	$ 29
Offsetting Counterparty Fair Value	11
Net Fair Value in the Consolidated Balance Sheets	18
Counterparty A
Change in unrealized gain (loss) on anticipated sales hedging:
Gross Fair Value	8
Offsetting Counterparty Fair Value	4
Net Fair Value in the Consolidated Balance Sheets	4
Counterparty B
Change in unrealized gain (loss) on anticipated sales hedging:
Gross Fair Value	3
Offsetting Counterparty Fair Value	1
Net Fair Value in the Consolidated Balance Sheets	2
Counterparty C
Change in unrealized gain (loss) on anticipated sales hedging:
Gross Fair Value	3
Offsetting Counterparty Fair Value	1
Net Fair Value in the Consolidated Balance Sheets	2
Counterparty D
Change in unrealized gain (loss) on anticipated sales hedging:
Gross Fair Value	5
Offsetting Counterparty Fair Value	3
Net Fair Value in the Consolidated Balance Sheets	2
Counterparty E
Change in unrealized gain (loss) on anticipated sales hedging:
Gross Fair Value	3
Offsetting Counterparty Fair Value	1
Net Fair Value in the Consolidated Balance Sheets	2
Counterparty F
Change in unrealized gain (loss) on anticipated sales hedging:
Gross Fair Value	3
Offsetting Counterparty Fair Value	1
Net Fair Value in the Consolidated Balance Sheets	2
Counterparty G
Change in unrealized gain (loss) on anticipated sales hedging:
Gross Fair Value	4
Offsetting Counterparty Fair Value	0
Net Fair Value in the Consolidated Balance Sheets	$ 4

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=82849420&loc=SL20226008-175313

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13495-108611

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=51824906&loc=SL20225862-175312

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13433-108611

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

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