Fair Value Measurements (Assets and Liabilities on a Nonrecurring Basis) (Details) - Nonrecurring [Member] - Level 3 [Member] - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying amount of direct investments in privately-held companies, impaired during the period	$ 5,000,000.0	$ 500,000	$ 6,300,000	$ 2,400,000
Fair value of direct investments in privately-held companies	4,600,000	100,000	4,600,000	400,000
Upward adjustment to one of the company's investments in a privately-held company	0	0	1,800,000	0
Other (Expense) Income, Net [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment charge	$ 400,000	$ 400,000	$ 1,700,000	$ 2,000,000.0