Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies, Revenue Recognition through Subsequent Events (Details)

v3.7.0.1
Summary of Significant Accounting Policies, Revenue Recognition through Subsequent Events (Details)
$ in Millions
2 Months Ended 3 Months Ended 6 Months Ended
Sep. 30, 2017
USD ($)
Jun. 30, 2017
USD ($)
Criteria
Mar. 31, 2017
shares
Jun. 30, 2017
USD ($)
Criteria
shares
Jun. 30, 2016
USD ($)
shares
Dec. 31, 2016
USD ($)
Revenue Recognition [Abstract]            
Number of criteria to be met for recognition of revenue | Criteria   4   4    
Short- Term Financing Obligation [Abstract]            
Short-term financing obligation   $ 15.2   $ 15.2   $ 15.6
Unused credits   90.3   $ 90.3   $ 90.0
Treasury Stock [Abstract]            
Stock repurchased during period, shares (in shares) | shares       730,000 335,000  
Stock repurchased during period, amount       $ 87.9 $ 30.0  
Recent Accounting Pronouncements [Abstract]            
Provision for income taxes   5.7   18.3    
Net cumulative-effect adjustment       2.1    
Accrued employee taxes   $ 0.8   $ 0.8    
Scenario, Forecast [Member]            
Subsequent Event [Line Items]            
Consulting expenses $ 6.0          
ShippingEasy [Member]            
Equity, Class of Treasury Stock [Line Items]            
Shares withheld to satisfy income tax obligations (in shares) | shares     6,670