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Convertible Senior Notes - Additional Information (Details)
$ / shares in Units, $ in Thousands
1 Months Ended 3 Months Ended 6 Months Ended
Mar. 31, 2018
USD ($)
Mar. 31, 2018
USD ($)
Jun. 30, 2018
USD ($)
d
SinkingFund
$ / shares
shares
Debt Instrument [Line Items]      
Net proceeds from offering $ 139,400   $ 139,438
Notes initial conversion rate of common stock | shares     25.4544
Conversion rate of common stock per principal amount of Notes | $ / shares     $ 1,000
Debt instrument conversion price per share | $ / shares     $ 39.29
Debt instrument shares issuable upon conversion | shares     3,700,000
Convertible notes, conversion start date     Jan. 01, 2023
Number of consecutive trading days | d     30
Debt discount recorded in additional paid-in-capital     $ 32,637
Issuance costs attributable to liability component     3,600
Issuance costs attributable to equity component     $ 1,100
Class A Common Stock      
Debt Instrument [Line Items]      
Debt instrument shares issuable upon conversion | shares     1,928,417
Initial strike price | $ / shares     39.29
Cap price | $ / shares     60.44
Cost of purchased capped calls     $ 17,100
Closing Price of common stock | $ / shares     $ 36.20
LIBOR | Interest Rate Swap      
Debt Instrument [Line Items]      
Derivative contract term   5 years  
Minimum      
Debt Instrument [Line Items]      
Number of trading days | d     20
Conversion Condition One      
Debt Instrument [Line Items]      
Number of consecutive trading days | d     30
Minimum percentage of conversion price     130.00%
Conversion Condition One | Minimum      
Debt Instrument [Line Items]      
Number of trading days | d     20
Conversion Condition Two      
Debt Instrument [Line Items]      
Number of consecutive trading days | d     5
Number of business days     5 days
Notes measurement maximum percentage     98.00%
Convertible Debt      
Debt Instrument [Line Items]      
Convertible senior notes $ 143,800 $ 143,800 $ 143,750
Convertible senior notes percentage 0.875% 0.875%  
Debt instrument due date Apr. 01, 2023    
Debt instrument, description Interest is payable semi-annually in arrears on April 1 and October 1 of each year, commencing on October 1, 2018.    
Convertible notes redemption period     Apr. 05, 2021
Number of trading days to provide notice of redemption     3 days
Redemption price, percentage     100.00%
Number of sinking fund provided for notes | SinkingFund     0
6.34% Convertible Notes      
Debt Instrument [Line Items]      
Estimated implied interest rate on notes     6.34%
Fair value of liability component     $ 110,000
Debt discount recorded in additional paid-in-capital     $ 33,800