Annual report pursuant to Section 13 and 15(d)

Schedule II: Valuation and Qualifying Accounts (Details)

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Schedule II: Valuation and Qualifying Accounts (Details) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Allowance for Doubtful Accounts      
Valuation And Qualifying Accounts Disclosure [Line Items]      
Balance at Beginning of Year $ 1,415 $ 1,869 $ 1,664
Additions 1,685 3,864 3,580
Deletions 2,677 4,418 2,575
Adjustments 270 100 (800)
Balance at End of Year 693 1,415 1,869
Allowance for Sales Returns      
Valuation And Qualifying Accounts Disclosure [Line Items]      
Balance at Beginning of Year 904 585 366
Additions 15,834 9,909 7,502
Deletions 15,848 9,590 7,283
Balance at End of Year 890 904 585
Allowance for Rental Revenue Adjustments      
Valuation And Qualifying Accounts Disclosure [Line Items]      
Balance at Beginning of Year 947 6,078 4,115
Additions 2,678 5,057 10,777
Deletions 2,917 10,088 9,614
Adjustments (270) (100) 800
Balance at End of Year 438 947 6,078
Allowance for Rental Asset Loss      
Valuation And Qualifying Accounts Disclosure [Line Items]      
Balance at Beginning of Year 754 725 850
Additions 408 561 455
Deletions 568 532 580
Balance at End of Year $ 594 $ 754 $ 725