Investments Other Segments and Holding Company (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Schedule of Investments [Line Items]
Investments	$ 9,945	$ 8,337
Other Segments and Holding Company
Schedule of Investments [Line Items]
Investments	738	1,470
Portion of unrealized (losses) gains that relates to equity securities still held	(421)	(339)	$ 67
Equity method investments | Other Segments and Holding Company
Schedule of Investments [Line Items]
Investments	201	143
Other investments | Other Segments and Holding Company
Schedule of Investments [Line Items]
Investments	$ 537	$ 1,327