Segment Information (Details 3) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Depreciation and amortization									$ (5,120)	$ (3,936)	$ (3,916)
Impairment of goodwill									(2,726)	0	0
Total other expenses, net									(2,133)	(1,469)	(1,313)
Income (loss) before income tax expense									(1,563)	540	1,020
Income tax (expense) benefit									(170)	849	(394)
Net (loss) income	$ (2,412)	$ 272	$ 292	$ 115	$ 1,117	$ 92	$ 17	$ 163	(1,733)	1,389	626
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total segment adjusted EBITDA									10,451	7,534	7,685
Unallocated amount to segment
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Regulatory Revenue									723	732	704
Depreciation and amortization									(5,120)	(3,936)	(3,916)
Impairment of goodwill									(2,726)	0	0
Other operating expenses									(2,758)	(2,321)	(2,140)
Total other expenses, net									$ (2,133)	$ (1,469)	$ (1,313)