Cash and Cash Equivalents (Tables)

12 Months Ended

Dec. 31, 2017

Cash and Cash Equivalents [Abstract]

Components of cash and cash equivalents

The following table summarizes the components of our cash and cash equivalents (amounts in millions):

	At December 31,
	2017		2016
Cash	$	269	$	286
Foreign government treasury bills	39		38
Money market funds	4,405		2,921
Cash and cash equivalents	$	4,713	$	3,245