Annual report pursuant to Section 13 and 15(d)

Composition of Certain Financial Statement Captions - Narrative (Details)

v3.6.0.2
Composition of Certain Financial Statement Captions - Narrative (Details)
 12 Months Ended
Dec. 31, 2016
USD ($)
security
Dec. 31, 2015
USD ($)
Dec. 31, 2014
USD ($)
Property, Plant and Equipment [Abstract]      
Number of owned securities that were in an unrealized loss position | security 30    
Unrealized losses deemed to be other-than-temporary $ 0    
Proceeds from sale of available-for-sale securities 3,507,000 $ 111,356,000 $ 0
Realized gain (loss) in connecting with sales of available-for-sale securities 0    
Prepaid content acquisition costs 46,310,000 2,099,000  
Property, Plant and Equipment [Line Items]      
Depreciation 34,200,000 20,400,000 14,700,000
Capitalized cost related to internal use software and website development costs 7,500,000    
Accumulated amortization $ 89,385,000 55,145,000  
Minimum      
Property, Plant and Equipment [Line Items]      
Expected useful lives (years) 3 years    
Maximum      
Property, Plant and Equipment [Line Items]      
Expected useful lives (years) 5 years    
Software developed for internal use      
Property, Plant and Equipment [Line Items]      
Capitalized cost related to internal use software and website development costs $ 25,700,000 6,300,000  
Accumulated amortization 9,300,000 4,000,000.0  
Amortization expense $ 5,300,000 2,200,000 $ 1,100,000
Software developed for internal use | Minimum      
Property, Plant and Equipment [Line Items]      
Expected useful lives (years) 3 years    
Software developed for internal use | Maximum      
Property, Plant and Equipment [Line Items]      
Expected useful lives (years) 5 years    
Other current assets      
Property, Plant and Equipment [Line Items]      
Receivables for the reimbursement of costs of leasehold improvements in connection with operating leases $ 9,100,000 $ 12,900,000