Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating activities
Net loss	$ (19.2)	$ (12.9)
Adjustments to reconcile net loss to cash used in operating activities:
Depreciation and amortization	3.4	2.4
Share-based compensation	25.1	15.9
Accretion and amortization related to marketable securities, net	0.1	0.1
Amortization of debt issuance costs	0.0	0.1
Other Noncash Expense	0.0	0.2
Changes in operating assets and liabilities:
Accounts receivable, net	6.8	2.2
Inventory	(10.9)	(2.4)
Prepaid and other assets	(1.0)	0.2
Accounts payable and accrued liabilities	3.7	1.6
Accrued payroll and related expenses	(8.2)	(5.1)
Deferred revenue	(0.2)	0.6
Deferred rent and other liabilities	0.2	0.5
Net cash (used in) provided by operating activities	(0.2)	3.4
Investing activities
Purchase of available-for-sale marketable securities	(10.8)	(22.6)
Proceeds from the maturity of available-for-sale marketable securities	11.1	4.7
Purchase of property and equipment	(11.5)	(8.0)
Net cash used in investing activities	(11.2)	(25.9)
Financing activities
Net proceeds from issuance of common stock	3.8	5.5
Repayment of long-term debt	(0.6)	(0.6)
Net cash provided by financing activities	3.2	4.9
Decrease in cash and cash equivalents	(8.2)	(17.6)
Cash and cash equivalents, beginning of period	86.1	71.8
Cash and cash equivalents, end of period	$ 77.9	$ 54.2