UNAUDITED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Statement of Cash Flows [Abstract]
Net income	[1]	$ 765	$ 607
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization		116	103
Provision for uncollectible accounts		40	29
Deferred income tax expense		89	9
Net unrealized gains on marketable equity securities		(451)	(55)
Stock-based compensation expense and other stock-based payments		78	71
Operating lease amortization		42	0
Amortization of debt discount and debt issuance costs		14	17
Contingent consideration fair value adjustment		7	0
Changes in assets and liabilities:
Accounts receivable		(24)	(96)
Prepaid expenses and other current assets		(669)	(709)
Accounts payable, accrued expenses and other current liabilities		561	632
Other long-term assets and liabilities		(418)	32
Net cash provided by operating activities		150	640
INVESTING ACTIVITIES:
Purchase of investments		(445)	(714)
Proceeds from sale and maturity of investments		2,665	2,481
Additions to property and equipment		(111)	(131)
Net cash provided by investing activities		2,109	1,636
FINANCING ACTIVITIES:
Proceeds from revolving credit facility		250	0
Repayments of short-term borrowings		(25)	0
Payments for conversion of senior notes		0	(1,487)
Payments for repurchase of common stock		(2,773)	(718)
Net cash used in financing activities		(2,548)	(2,205)
Effect of exchange rate changes on cash and cash equivalents and restricted cash and cash equivalents		(2)	11
Net (decrease) increase in cash and cash equivalents and restricted cash and cash equivalents		(291)	82
Total cash and cash equivalents and restricted cash and cash equivalents, beginning of period		2,645	2,563
Total cash and cash equivalents and restricted cash and cash equivalents, end of period		2,354	2,645
SUPPLEMENTAL CASH FLOW INFORMATION:
Cash paid during the period for income taxes		816	784
Cash paid during the period for interest		$ 68	$ 74

[1] The Company realized net gains of $1 million for the three months ended March 31, 2019 from sales of investments in debt securities.