Condensed Consolidated Statements of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash Flows from Operating Activities:
Net income (loss)	$ 37.4	$ (102.1)
Reconciliation of net income (loss) to net cash provided by (used in) operating activities:
Share-based compensation expense	22.8	15.8
Depreciation	2.1	1.6
Amortization of debt discount	5.0	4.6
Amortization of debt issuance costs	0.3	0.3
Change in fair value of equity security investments	16.5	(1.7)
Other	0.4	(0.2)
Change in operating assets and liabilities:
Accounts receivable	(22.1)	(15.7)
Inventory	(3.9)	(1.8)
Accounts payable and accrued liabilities	(16.2)	(16.6)
Other current assets and liabilities, net	(4.1)	3.3
Net cash provided by (used in) operating activities	38.2	(112.5)
Cash Flows from Investing Activities:
Purchases of debt securities available-for-sale	(172.0)	(116.3)
Sales and maturities of debt securities available-for-sale	206.5	215.9
Purchases of equity securities		(54.7)
Purchases of property and equipment	(1.3)	(3.9)
Net cash provided by investing activities	33.2	41.0
Cash Flows from Financing Activities:
Issuance of common stock	3.3	2.6
Net cash provided by financing activities	3.3	2.6
Change in cash and cash equivalents and restricted cash	74.7	(68.9)
Cash and cash equivalents and restricted cash at beginning of period	115.5	147.2
Cash and cash equivalents and restricted cash at end of period	190.2	78.3
Supplemental Disclosure:
Non-cash capital expenditures	$ 0.8	$ 0.6