Consolidated Statements Of Operations (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Revenues	$ 4,110	$ 3,912
Operating expenses:
Cost of revenues (exclusive of depreciation and amortization expense shown separately below)	2,575	2,401
Selling, general and administrative expenses	873	711
Depreciation and amortization expense	123	107
Income from operations	539	693
Other income (expense), net:
Interest income	48	41
Interest expense	(7)	(6)
Foreign currency exchange gains (losses), net	2	(31)
Other, net	1	0
Total other income (expense), net	44	4
Income before provision for income taxes	583	697
Provision for income taxes	(142)	(177)
Net income	$ 441	$ 520
Basic earnings per share (usd per share)	$ 0.77	$ 0.89
Diluted earnings per share (usd per share)	$ 0.77	$ 0.88
Weighted average number of common shares outstanding - Basic (shares)	573	587
Dilutive effect of shares issuable under stock-based compensation plans (shares)	2	2
Weighted average number of common shares outstanding - Diluted (shares)	575	589