Fair Value Measurements - Narrative (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Goodwill and intangible impairment	$ 0
Equity securities without readily determinable fair value, impairment	0
Equity securities without readily determinable fair value, upward adjustment	0
Equity securities without readily determinable fair value, downward adjustment	0
Contract manufacturer deposit (non-interest bearing)	47,600,000
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial and nonfinancial liabilities, fair value disclosure	5,800,000	$ 7,100,000
Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial and nonfinancial liabilities, fair value disclosure	0	0
Significant Other Unobservable Remaining Inputs (Level 3) | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial and nonfinancial liabilities, fair value disclosure	0	0
Significant Other Observable Remaining Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term and long-term debt, fair value	1,856,200,000	2,158,700,000
Significant Other Observable Remaining Inputs (Level 2) | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial and nonfinancial liabilities, fair value disclosure	5,800,000	7,100,000
Privately-held debt and redeemable preferred stock securities | Significant Other Unobservable Remaining Inputs (Level 3) | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized gain (loss) on investments	0
Junos Pulse
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Note receivable	$ 69,000,000	$ 69,000,000