Fair Value Measurements - Narrative (Details) - USD ($) $ in Thousands		1 Months Ended	9 Months Ended		12 Months Ended
	Apr. 20, 2016	Nov. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2019	Mar. 31, 2018	Sep. 30, 2017	Mar. 31, 2017	Dec. 28, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration for business acquisition - current portion			$ 0					$ 2,889
Payment of contingent consideration for business acquisition			5,000	$ 0
Trading investments for deferred compensation plan			17,998					15,043
Cost method investments at cost			7,100					7,400
Lifesize | Preferred Stock
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of cost method investment									$ 5,600
Jaybird | Revenue Growth
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Maximum earn-out	$ 45,000
Earn-out payments net revenue target period	2 years
Jaybird | Revenue Growth | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate for value measurement	16.00%
Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquisition-related contingent consideration included in accrued and other current liabilities and other non-current liabilities			0					0
Trading investments for deferred compensation plan			17,998					15,043
Fair Value, Measurements, Recurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquisition-related contingent consideration included in accrued and other current liabilities and other non-current liabilities			0					9,908
Trading investments for deferred compensation plan			$ 0					$ 0
Fair Value, Measurements, Recurring | Jaybird | Revenue Growth
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Acquisition-related contingent consideration included in accrued and other current liabilities and other non-current liabilities	$ 18,000
Scenario, Forecast | Jaybird | Revenue Growth
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Earn-out payments (up to)					$ 20,000	$ 25,000
Contingent Consideration | Earn Out Payment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration for business acquisition - current portion							$ 5,000
Payment of contingent consideration for business acquisition		$ 5,000