Annual report pursuant to Section 13 and 15(d)

Summary of Significant Accounting Policies - Narrative (Details)

v3.20.4
Summary of Significant Accounting Policies - Narrative (Details)
$ in Thousands
3 Months Ended 12 Months Ended
Mar. 31, 2019
shares
Mar. 31, 2018
shares
Dec. 31, 2020
USD ($)
segment
shares
Dec. 31, 2019
USD ($)
shares
Dec. 31, 2018
USD ($)
shares
Aug. 31, 2018
Aug. 15, 2018
Summary Of Significant Accounting Policies [Line Items]              
Allowances for uncollectible accounts     $ 11,900 $ 6,900      
Advertising and tradeshow costs     80,000 60,900 $ 51,600    
Revenue recognized     7,900 6,300      
Inventory, net     3,600 3,900      
Prepaid postage and shipping labels     $ 82,400 17,400      
Number of operating segments | segment     2        
Short-term financing obligations     $ 15,071 982      
Unused credit     $ 57,000 $ 69,500      
Treasury shares acquired (in shares) | shares     299,000 720,000 755,000    
Treasury stock, value, acquired, cost method     $ 54,621 $ 64,889 $ 136,840    
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        
MetaPack              
Summary Of Significant Accounting Policies [Line Items]              
Business acquisition, percentage of voting interests acquired           100.00% 100.00%
ShippingEasy              
Summary Of Significant Accounting Policies [Line Items]              
Shares withheld to satisfy income tax obligations (in shares) | shares 1,039 21,076