Investments and Related Matters Other Segments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule of Investments [Line Items]
Investments	$ 8,337	$ 10,015
Other Segments and Holding Company
Schedule of Investments [Line Items]
Investments	1,470	483
Portion of unrealized (losses) gains that relates to equity securities still held	(339)	67	$ 0
Equity method investments | Other Segments and Holding Company
Schedule of Investments [Line Items]
Investments	143	83
Other investments | Other Segments and Holding Company
Schedule of Investments [Line Items]
Investments	$ 1,327	$ 400