Supplemental Cash Flow Information Supplemental Cash Flow Information - Narrative (Details) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018
Supplemental Cash Flow Information [Abstract]
Transfer from Investments	$ 62	$ 13

Value of investments transferred from the entity's investments in noncash transactions.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 4
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration