Condensed Consolidated Statements Of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash flows from operating activities:
Net income	$ 441	$ 520
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	133	117
Provision for doubtful accounts	14	2
Deferred income taxes	(42)	2
Stock-based compensation expense	66	59
Other	(21)	23
Changes in assets and liabilities:
Trade accounts receivable	(131)	(273)
Other current and noncurrent assets	90	247
Accounts payable	49	86
Deferred revenues, current and noncurrent	56	(2)
Other current and noncurrent liabilities	(386)	(393)
Net cash provided by operating activities	269	388
Cash flows from investing activities:
Purchases of property and equipment	(106)	(96)
Purchases of available-for-sale investment securities	(243)	(300)
Proceeds from maturity or sale of available-for-sale investment securities	650	193
Purchases of held-to-maturity investment securities	(94)	(222)
Proceeds from maturity of held-to-maturity investment securities	348	171
Purchases of other investments	(31)	(31)
Proceeds from maturity or sale of other investments	29	59
Payments for business combinations, net of cash acquired	(197)	(1)
Net cash provided by (used in) investing activities	356	(227)
Cash flows from financing activities:
Issuance of common stock under stock-based compensation plans	50	60
Repurchases of common stock	(771)	(316)
Repayment of term loan borrowings and finance lease obligations	(2)	(39)
Net change in notes outstanding under the revolving credit facility	0	(75)
Dividends paid	(116)	(118)
Net cash (used in) financing activities	(839)	(488)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	3	1
(Decrease) in cash, cash equivalents and restricted cash	(211)	(326)
Cash and cash equivalents, beginning of year	1,161	1,925
Cash, cash equivalents and restricted cash, end of period	$ 950	$ 1,599