Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Narrative (Details)

v3.19.3.a.u2
Summary of Significant Accounting Policies - Narrative (Details)
$ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2019
shares
Mar. 31, 2018
shares
Mar. 31, 2017
shares
Dec. 31, 2019
USD ($)
segment
shares
Dec. 31, 2018
USD ($)
shares
Dec. 31, 2017
USD ($)
shares
Jan. 01, 2019
USD ($)
Summary Of Significant Accounting Policies [Line Items]              
Allowances for uncollectible accounts       $ 6,900 $ 6,600    
Allowance for doubtful accounts receivable, period increase (decrease)       400 2,600    
Advertising and tradeshow costs       60,900 51,600 $ 45,000  
Revenue recognized       6,300 2,900    
Inventory, net       3,900 3,800    
Prepaid postage and shipping labels       $ 17,400 4,800    
Number of operating segments | segment       2      
Short-term financing obligations       $ 982 23,800    
Unused credit       $ 69,500 $ 96,700    
Treasury shares acquired (in shares) | shares       720,000 755,000 988,000  
Treasury stock, value, acquired, cost method       $ 64,889 $ 136,840 $ 133,765  
Operating lease, right-of-use asset       17,697      
Operating lease, liability       $ 18,803      
Minimum | Furniture, Fixtures and Equipment              
Summary Of Significant Accounting Policies [Line Items]              
Estimated useful life       3 years      
Minimum | Building and Building Improvements              
Summary Of Significant Accounting Policies [Line Items]              
Estimated useful life       10 years      
Maximum | Furniture, Fixtures and Equipment              
Summary Of Significant Accounting Policies [Line Items]              
Estimated useful life       5 years      
Maximum | Building and Building Improvements              
Summary Of Significant Accounting Policies [Line Items]              
Estimated useful life       40 years      
Accounting Standards Update 2016-02              
Summary Of Significant Accounting Policies [Line Items]              
Operating lease, right-of-use asset             $ 11,800
Operating lease, liability             $ 13,600
ShippingEasy              
Summary Of Significant Accounting Policies [Line Items]              
Shares withheld to satisfy income tax obligations (in shares) | shares 1,039 21,076 6,670