Stockholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions			6 Months Ended		137 Months Ended
		Jul. 15, 2019	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Aggregate Board of Directors repurchase authorizations (in $ millions)	[1]		$ 1,500	$ 0	$ 5,366
Common stock, par value			$ 0.0001		$ 0.0001	$ 0.0001
Subsequent Event [Member]
Class of Stock [Line Items]
Common Stock, Dividends, Per Share, Declared		$ 0.62
Dividends, Common Stock, Cash		$ 77

[1] These authorizations give management discretion in determining the timing and conditions under which shares may be repurchased. This repurchase program began in February 2008 and does not have an expiration date.