Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Operating activities:
Net income	$ 474	$ 511	$ 2,554
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	138	134
Stock-based compensation	29	34
Deferred taxes	(6)	28
Cetip realized investment gain, net	0	(176)
Other	1	(1)
Changes in assets and liabilities:
Customer accounts receivable	(259)	(240)
Other current and non-current assets	(32)	(3)
Section 31 fees payable	(8)	(40)
Deferred revenue	343	327
Other current and non-current liabilities	(107)	37
Total adjustments	99	100
Net cash provided by operating activities	573	611
Investing activities:
Capital expenditures	(14)	(32)
Capitalized software development costs	(37)	(34)
Cash paid for acquisitions, net of cash received for divestiture	(400)	22
Purchases of investments	(304)	0
Net cash used in investing activities	(755)	(44)
Financing activities:
Proceeds from (repayments of) commercial paper, net	789	(117)
Repurchases of common stock	(300)	(229)
Dividends to stockholders	(140)	(120)
Payments relating to treasury shares received for restricted stock tax payments and stock option exercises	(72)	(77)
Other	(7)	(8)
Net cash provided by (used in) financing activities	270	(551)
Effect of exchange rate changes on cash, cash equivalents and restricted cash and cash equivalents	2	1
Net increase in cash, cash equivalents, and restricted cash and cash equivalents	90	17
Cash, cash equivalents, and restricted cash and cash equivalents, beginning of period	1,568	1,350	1,350
Cash, cash equivalents, and restricted cash and cash equivalents, end of period	1,658	1,367	$ 1,568
Supplemental cash flow disclosure:
Cash paid for income taxes	144	65
Cash paid for interest	$ 27	$ 7