Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net income	$ 713.7	$ 651.6	$ 340.1
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	31.6	32.9	32.2
Share-based compensation expense	12.1	280.3	190.1
Gain on sale of intangible asset		(350.0)
Other	9.5	7.5	24.2
Excess tax benefits from share-based compensation	(5.9)	(37.4)	(30.8)
Changes in operating assets and liabilities:
Accounts receivable	(21.7)	(30.5)	(35.7)
Inventories	(24.5)	(6.8)	(21.0)
Accounts payable and accrued expenses	0.6	17.0	(6.8)
Other assets and liabilities	(71.8)	(181.8)	(137.0)
Net cash provided by operating activities	643.6	382.8	355.3
Cash flows from investing activities:
Purchases of property, plant and equipment	(38.0)	(49.8)	(47.4)
Purchases of held-to-maturity investments	(0.8)	(62.8)	(118.7)
Maturities of held-to-maturity investments	130.4	320.4	549.6
Gain on sale of intangible asset		350.0
Purchase of investments held at cost	(36.0)	(54.2)	(45.0)
Purchase of investments under the equity method	(2.1)
Intangible assets acquired, net	(5.2)
Net cash provided by investing activities	48.3	503.6	338.5
Cash flows from financing activities:
Principal payments of debt	(8.8)	(133.2)	(177.8)
Payments of debt issuance costs	(6.8)
Payments to repurchase common stock	(500.0)	(394.5)	(483.1)
Proceeds from line of credit			140.0
Payments on line of credit			(140.0)
Proceeds from exercise of stock options	7.7	39.3	50.2
Issuance of stock under employee stock purchase plan	4.3	4.0	3.3
Excess tax benefits from share-based compensation	5.9	37.4	30.8
Net cash used in financing activities	(497.7)	(447.0)	(576.6)
Effect of exchange rate changes on cash and cash equivalents	(3.0)	(5.3)	(3.8)
Net increase in cash and cash equivalents	191.2	434.1	113.4
Cash and cash equivalents, beginning of year	831.8	397.7	284.3
Cash and cash equivalents, end of year	1,023.0	831.8	397.7
Supplemental cash flow information:
Cash paid for interest	1.5	1.0	5.5
Cash paid for income taxes	362.4	293.3	195.6
Non-cash investing and financing activities:
Acquisitions-non-cash consideration			5.2
Non-cash additions to property, plant and equipment	2.9	1.1	3.2
Issuance of common stock upon conversion of convertible notes	$ 7.5	$ 321.8	$ 189.3