Consolidated Statements of Changes in Equity - USD ($) $ in Millions		Total	Member's Equity	Accumulated Other Comprehensive Income (Loss)
Balance at Dec. 31, 2017		$ 43,009	$ 42,778	$ 231
Cash distributions		(1,100)	(1,100)	0
Comprehensive income (loss), net of tax		1,146	1,145	1
Balance at Mar. 31, 2018		43,052	42,795	257
Cumulative Effect of New Accounting Principle in Period of Adoption | Difference between Revenue Guidance in Effect before and after Topic 606	[1]	(3)	(3)	0
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2016-01	[2]	0	1	(1)
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2018-02	[3]	0	(26)	26
Balance at Dec. 31, 2018		42,649	42,519	130
Cash distributions		(1,200)	(1,200)	0
Comprehensive income (loss), net of tax		1,315	1,253	62
Balance at Mar. 31, 2019		$ 42,764	$ 42,572	$ 192

[1] Accounting Standards Codification Topic 606 - Revenue from Contracts with Customers

[2] Accounting Standards Update No. 2016-01 Financial Instruments - Recognition and Measurement of Financial Assets and Financial Liabilities

[3] Accounting Standards Update No. 2018-02 Income Statement - Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income