Basis of Presentation and Significant Accounting Policies (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
	Jan. 01, 2018	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Basis of Presentation and Significant Accounting Policies (Textual)
Operating expenses (excluding depreciation and amortization expense)		$ 1,110	$ 1,111	$ 2,246	$ 2,235
General and administrative expenses (excluding depreciation and amortization expense)		$ 248	175	486	367
Reclassification of stranded income tax effects of Tax Reform to retained earnings per ASU 2018-02				$ 91	0
Accounting Standards Update 2017-07 [Member]
Basis of Presentation and Significant Accounting Policies (Textual)
Operating expenses (excluding depreciation and amortization expense)			14		21
General and administrative expenses (excluding depreciation and amortization expense)			$ (3)		$ (1)
Accounting Standards Update 2018-02 [Member]
Basis of Presentation and Significant Accounting Policies (Textual)
Reclassification of stranded income tax effects of Tax Reform to retained earnings per ASU 2018-02	$ 91
Minimum [Member]
Basis of Presentation and Significant Accounting Policies (Textual)
Typical post-delivery payment terms (in days)				2 days
Maximum [Member]
Basis of Presentation and Significant Accounting Policies (Textual)
Typical post-delivery payment terms (in days)				10 days