Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Cash Flows [Abstract]
Net income	$ 177	$ 168
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	53	45
Share-based compensation	15	15
Deferred income taxes	(9)	29
Net income from unconsolidated investees	(2)	(4)
Other reconciling items included in net income	3	7
Net change in operating assets and liabilities, net of effects of acquisitions:
Receivables, net	(127)	(29)
Other assets	39	(7)
Accounts payable and accrued expenses	65	12
Section 31 fees payable to SEC	0	(27)
Accrued personnel costs	(59)	(98)
Deferred revenue	208	152
Other liabilities	1	(19)
Net assets held for sale	11	0
Net cash provided by operating activities	375	244
Cash flows from investing activities:
Purchases of trading securities	(70)	(93)
Proceeds from sales and redemptions of trading securities	75	120
Purchases of available-for-sale investment securities	(3)	(5)
Proceeds from maturities of available-for-sale investment securities	6	6
Purchases of property and equipment	(16)	(36)
Net cash used in investing activities	(8)	(8)
Cash flows from financing activities:
Repayments of commercial paper, net	(18)	0
Repayments of long-term debt	(115)	0
Cash paid for repurchase of common stock	(99)	(156)
Cash dividends paid	(63)	(53)
Proceeds received from employee stock activity	0	1
Payments related to employee shares withheld for taxes	(42)	(47)
Proceeds of customer funds	0	63
Net cash used in financing activities	(337)	(192)
Effect of exchange rate changes on cash and cash equivalents and restricted cash	0	2
Net increase in cash and cash equivalents and restricted cash	30	46
Cash and cash equivalents and restricted cash at beginning of period	399	418
Cash and cash equivalents and restricted cash at end of period	429	464
Cash paid for:
Interest	33	29
Income taxes, net of refund	$ 27	$ 26