Commitments and Contingencies - Narrative (Details) $ in Millions		12 Months Ended
	Jan. 19, 2018 USD ($)	Dec. 31, 2017 lawsuit	Dec. 31, 2015 defendant	Mar. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)	Feb. 16, 2016 lawsuit
Jawbone [Member]
Loss Contingencies [Line Items]
Number of employees additional named as defendants | defendant			6
Heart Rage Tracking [Member]
Loss Contingencies [Line Items]
Number of pending claims | lawsuit						2
PurePulse Class Action Lawsuit [Member]
Loss Contingencies [Line Items]
Number of pending claims | lawsuit		7
Settlement amount award to other party	$ 33.3
Loss Contingency, Pending Claims, Consolidated | lawsuit		3
Letter of Credit [Member]
Loss Contingencies [Line Items]
Long-term Line of Credit				$ 36.6	$ 36.9
Accrued liabilities [Member]
Loss Contingencies [Line Items]
Remaining minimum amount committed				5.9
Purchase Commitment [Member]
Loss Contingencies [Line Items]
Remaining minimum amount committed				605.8
Purchase Commitment [Member] | Accrued liabilities [Member]
Loss Contingencies [Line Items]
Remaining minimum amount committed				12.7
Purchase Commitment to Third Party Hosting Provider [Member]
Loss Contingencies [Line Items]
Remaining minimum amount committed				$ 185.0