Supplemental Disclosures of Cash Flow (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental Disclosures of Cash Flow Data [Abstract]
Interest paid	$ 154	$ 123	$ 91
Income taxes paid (received)	192	215	121
Significant non-cash investing and financing transactions:
Acquisition of note receivable from affiliate	31	74	42
Investments received in financing transactions	263
Carrying value of asset, Exchanges of surplus note for promissory note with affiliate	58	109	124
Carrying value of liability, Exchange of surplus note for promissory note with affiliate	(58)	(109)	(124)
Net asset (liability) from exchange