Quarterly report pursuant to Section 13 or 15(d)

Commitments and Contingencies - Commitments (Details)

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Commitments and Contingencies - Commitments (Details) - USD ($)
$ in Millions
3 Months Ended
Jul. 27, 2017
Mar. 31, 2018
Mar. 31, 2017
Commitments and Contingencies Disclosure [Abstract]      
Rent expense   $ 2.0 $ 1.8
Emerging Markets Communications LLC      
Long-term Commitment [Line Items]      
Common stock issued for acquisition (in shares) 5,080,049    
Line of Credit      
Long-term Commitment [Line Items]      
Letters of credit outstanding   6.8  
Line of Credit | Letters of Credit      
Long-term Commitment [Line Items]      
Letters of credit outstanding   $ 6.2