CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities:
Net income	$ 122.6	$ 441.6
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	15.6	15.6
Share-based compensation benefit	(21.0)	(143.1)
Impairment of cost method investment	46.5
Estimated loss contingency	210.0
Other	(9.9)	1.5
Excess tax benefits from share-based compensation		(3.5)
Changes in operating assets and liabilities:
Accounts receivable	(59.4)	(45.3)
Inventories	(14.8)	(8.8)
Accounts payable and accrued expenses	20.8	19.8
Other assets and liabilities	(8.9)	(26.3)
Net cash provided by operating activities	301.5	251.5
Cash flows from investing activities:
Purchases of property, plant and equipment	(36.5)	(14.2)
Purchases of held-to-maturity and other investments	(25.1)	(0.8)
Maturities of held-to-maturity investments	26.1	49.6
Purchases of available-for-sale investments	(296.5)
Purchase of investments held at cost	(25.1)	(7.6)
Purchase of investments under the equity method		(2.1)
Consolidation of variable interest entity	0.1
Intangible assets acquired		(5.2)
Net cash (used in) provided by investing activities	(357.0)	19.7
Cash flows from financing activities:
Principal payments of debt		(7.9)
Payments of debt issuance costs	(0.7)	(6.8)
Payments to repurchase common stock	(250.0)	(259.7)
Proceeds from line of credit	250.0
Proceeds from the exercise of stock options	36.6	5.0
Issuance of stock under employee stock purchase plan	2.1	2.2
Excess tax benefits from share-based compensation		3.5
Net cash provided by (used in) financing activities	38.0	(263.7)
Effect of exchange rate changes on cash and cash equivalents	0.4	(1.8)
Net (decrease) increase in cash and cash equivalents	(17.1)	5.7
Cash and cash equivalents, beginning of period	1,023.0	831.8
Cash and cash equivalents, end of period	1,005.9	837.5
Supplemental cash flow information:
Cash paid for interest	1.6	0.1
Cash paid for income taxes	157.9	222.0
Non-cash investing and financing activities:
Non-cash additions to property, plant and equipment	$ 7.0	3.4
Issuance of common stock upon conversion of convertible notes		$ 6.1