Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities
Net income	$ 2,542	$ 1,449	$ 1,295
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	535	610	374
Stock-based compensation	135	124	111
Deferred taxes	(651)	114	(108)
Cetip realized investment gain, net	(114)	0	0
Trayport gain, net	110	0	0
Amortization of fair market value premium on NYSE Notes	0	0	(23)
Other	(22)	(6)	(17)
Changes in assets and liabilities:
Customer accounts receivable	(135)	(65)	(45)
Other current and non-current assets	(24)	7	(5)
Section 31 fees payable	(2)	14	(21)
Deferred revenue	17	42	27
Other current and non-current liabilities	(86)	(140)	(277)
Total adjustments	(457)	700	16
Net cash provided by operating activities	2,085	2,149	1,311
Investing activities
Capital expenditures	(220)	(250)	(190)
Capitalized software development costs	(137)	(115)	(87)
Proceeds from sale of Cetip, net	438	0	0
Cash paid for acquisitions, net of cash acquired	(423)	(425)	(3,751)
Cash received from divestitures	761	0	0
Purchases of cost and equity method investments	(327)	(70)	(60)
Proceeds from term deposits	0	0	1,089
Other	0	0	(5)
Net cash provided by (used in) investing activities	92	(860)	(3,004)
Financing activities
Proceeds from debt facilities, net	984	0	2,472
Repayments of debt facilities	(850)	0	(1,028)
Proceeds from (repayments of) commercial paper, net	(409)	(949)	1,686
Dividends to shareholders	(476)	(409)	(331)
Repurchases of common stock	(949)	(50)	(660)
Payments relating to treasury shares received for restricted stock tax payments and stock option exercises	(88)	(54)	(45)
Acquisition of non-controlling interest and redeemable non-controlling interest	(174)	0	0
Purchase of subsidiary shares from non-controlling interest	0	0	(128)
Other	(9)	0	10
Net cash provided by (used in) financing activities	(1,971)	(1,462)	1,976
Effect of exchange rate changes on cash, cash equivalents, and restricted cash and cash equivalents	12	(24)	(14)
Net increase (decrease) in cash, cash equivalents, and restricted cash and cash equivalents	218	(197)	269
Cash and cash equivalents, beginning of the year	1,350	1,547	1,278
Cash and cash equivalents, end of the year	1,568	1,350	1,547
Supplemental cash flow disclosure
Cash paid for income taxes	594	460	542
Cash paid for interest	171	170	123
Supplemental non-cash investing and financing activities
Common stock and vested stock options issued for acquisitions	0	0	2,197
Treasury stock retirement	$ 0	$ 1,512	$ 0