Annual report pursuant to Section 13 and 15(d)

Commitments and Contingencies - Additional Information (Detail)

v3.8.0.1
Commitments and Contingencies - Additional Information (Detail)
$ in Millions
 3 Months Ended 12 Months Ended
Jun. 30, 2017
USD ($)
Dec. 31, 2017
USD ($)
Option
Dec. 31, 2016
USD ($)
Dec. 31, 2015
USD ($)
Contingencies And Commitments [Line Items]        
Lease exit expense $ 1.0 $ 2.2    
Interest Expense   0.6    
Lease exit accrued cost   $ 1.6    
Operating lease term for dealership facilities, minimum   15 years    
Operating lease term for dealership facilities, maximum   20 years    
Operating lease number of renewal options, minimum | Option   1    
Operating lease number of renewal options, maximum | Option   2    
Operating lease period of renewal options, minimum   5 years    
Operating lease period of renewal options, maximum   10 years    
Percentage of lease facility based on capitalization rates   10.00%    
Lease expense for continuing operation   $ 100.6 $ 94.6 $ 98.2
Lease expense from discontinuing operation net of lease exit accrual adjustments   1.3 0.9 1.4
Leases, net contingent rent benefit related to decrease in interest rates from continuing operation   1.7 1.8 2.0
Leases net contingent rent benefit related to decrease in interest rates from discontinuing operation   0.1 0.1 $ 0.1
Obligations under subleases, if subleases do not perform   47.7    
Maximum exposure associated with general indemnifications   $ 5.0    
General indemnifications expiration period   1 year    
Contingent liability reserve balance after reduction   $ 2.8    
Other Accrued Liabilities [Member]        
Contingencies And Commitments [Line Items]        
Amount reserved for pending proceedings   3.0 0.3  
Other Long-Term Liabilities [Member]        
Contingencies And Commitments [Line Items]        
Amount reserved for pending proceedings   $ 0.2 $ 0.2  
Dealership [Member]        
Contingencies And Commitments [Line Items]        
Joint venture ownership percentage   50.00%