Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net income	$ 1,246,000,000	$ 930,000,000	$ 712,000,000
Adjustment for discontinued operations	(14,000,000)	0	0
Adjustments to reconcile net income to net cash provided by operating activities from continuing operations:
Depreciation and other amortization	274,000,000	253,000,000	223,000,000
Amortization of acquisition-related intangible assets	159,000,000	158,000,000	194,000,000
Share-based compensation	63,000,000	68,000,000	65,000,000
Excess tax benefits from share-based awards	0	(51,000,000)	(38,000,000)
Deferred income taxes	(247,000,000)	21,000,000	20,000,000
Income from investment in unconsolidated affiliate	(32,000,000)	(147,000,000)	(32,000,000)
Dividends from unconsolidated affiliate	45,000,000	151,000,000	36,000,000
Non-cash impairment charges	18,000,000	17,000,000	6,000,000
Gain on sale of business	(10,000,000)	0	0
Loss on early debt extinguishment	0	0	85,000,000
Other operating activities	(4,000,000)	(2,000,000)	(1,000,000)
Changes in assets and liabilities, net of effects from acquisitions:
Trade accounts receivable	(75,000,000)	(88,000,000)	(2,000,000)
Prepaid expenses and other assets	(55,000,000)	(68,000,000)	(66,000,000)
Accounts payable and other liabilities	54,000,000	178,000,000	148,000,000
Deferred revenue	61,000,000	11,000,000	(4,000,000)
Net cash provided by operating activities from continuing operations	1,483,000,000	1,431,000,000	1,346,000,000
Cash flows from investing activities:
Capital expenditures, including capitalization of software costs	(287,000,000)	(290,000,000)	(359,000,000)
Payments for acquisitions of businesses, net of cash acquired	(384,000,000)	(265,000,000)	0
Proceeds from sale of business	17,000,000	0	0
Purchases of investments	(10,000,000)	(1,000,000)	(4,000,000)
Other investing activities	7,000,000	2,000,000	3,000,000
Net cash used in investing activities from continuing operations	(657,000,000)	(554,000,000)	(360,000,000)
Cash flows from financing activities:
Debt proceeds	2,310,000,000	2,126,000,000	3,121,000,000
Debt repayments, including redemption and other costs	(1,985,000,000)	(1,863,000,000)	(2,707,000,000)
Proceeds from issuance of treasury stock	78,000,000	79,000,000	71,000,000
Purchases of treasury stock, including employee shares withheld for tax obligations	(1,223,000,000)	(1,245,000,000)	(1,522,000,000)
Excess tax benefits from share-based awards	0	51,000,000	38,000,000
Other financing activities	0	0	(6,000,000)
Net cash used in financing activities from continuing operations	(820,000,000)	(852,000,000)	(1,005,000,000)
Net change in cash and cash equivalents from continuing operations	6,000,000	25,000,000	(19,000,000)
Net cash flows from discontinued operations provided by operating activities	19,000,000	0	0
Cash and cash equivalents, beginning balance	300,000,000	275,000,000	294,000,000
Cash and cash equivalents, ending balance	$ 325,000,000	$ 300,000,000	$ 275,000,000