Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities:
Net income	$ 91.4	$ 80.2
Adjustments to reconcile net income to net cash provided by operating activities:
Share-based compensation expense	51.8	46.0
Depreciation, amortization, and accretion	47.0	47.5
Restructuring and other charges	0.0	1.4
Deferred income taxes	21.1	11.3
Loss (gain) on investments, net	5.4	(0.6)
Excess tax benefits from share-based compensation	0.0	(1.7)
Changes in operating assets and liabilities, net of effects from acquisitions:
Accounts receivable, net	(3.2)	54.2
Prepaid expenses and other assets	(59.6)	(21.8)
Accounts payable	69.8	(7.8)
Accrued compensation	(89.3)	(54.1)
Income taxes payable	(24.2)	14.1
Other accrued liabilities	(29.8)	(48.4)
Deferred revenue	92.0	99.0
Net cash provided by operating activities	172.4	219.3
Cash flows from investing activities:
Purchases of property and equipment	(49.3)	(44.2)
Purchases of available-for-sale investments	(360.7)	(398.8)
Proceeds from sales of available-for-sale investments	286.2	169.5
Proceeds from maturities of available-for-sale investments	79.6	57.3
Purchases of trading investments	(2.5)	(1.9)
Purchases of privately-held investments	(10.5)	(3.2)
Net cash used in investing activities	(57.2)	(221.3)
Cash flows from financing activities:
Proceeds from issuance of common stock	32.0	31.8
Purchases and retirement of common stock	(83.4)	(402.4)
Issuance of long-term debt, net	494.0	594.6
Repayment of long-term debt	(300.0)	0.0
Payment for capital lease obligation	0.0	0.4
Excess tax benefits from share-based compensation	0.0	1.7
Payment of cash dividends	(38.3)	(40.8)
Net cash provided by financing activities	104.3	185.3
Effect of foreign currency exchange rates on cash and cash equivalents	5.6	(12.1)
Net increase in cash and cash equivalents	225.1	171.2
Cash and cash equivalents at beginning of period	1,420.9	1,639.6
Cash and cash equivalents at end of period	$ 1,646.0	$ 1,810.8