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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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The cash outflow associated with the purchase of all investments (debt, security, other) during the period.

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Amount of cash inflow from sale of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Marketable Securities and Equity Investments Marketable Securities and Equity Investments - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Summary of cash, cash equivalents and marketable securities
Other-than-temporary declines in fair value of available-for-sale debt securities	$ 0	$ 0	$ 0
Gross realized gains or losses	0	$ 0	$ 0
Unrealized gains to other (expense) income, net	2,600,000
Other assets
Summary of cash, cash equivalents and marketable securities
Equity securities without readily determinable fair value, amount	13,600,000
CRISPR Therapeutics
Summary of cash, cash equivalents and marketable securities
Marketable securities, fair value, investment in common stock	153,700,000
Unrealized gains to other (expense) income, net	9,000,000
Payments to acquire investment	69,900,000
Moderna Therapeutics, Inc.
Summary of cash, cash equivalents and marketable securities
Marketable securities, fair value, investment in common stock	13,600,000
Unrealized gains to other (expense) income, net	$ 6,500,000