Shares and Stockholders' Equity (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019
Shares and Stockholders' Equity [Abstract]
Deferred compensation plan mark to market adjustment	$ 18	$ (7)
Outstanding warrants			0
Shares issuable per warrant			1