Annual report pursuant to Section 13 and 15(d)

Inventories and Related Notes Payable - Floor Plan - Additional Information (Detail)

v2.4.1.9
Inventories and Related Notes Payable - Floor Plan - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Inventory Disclosure [Abstract]      
Average interest rate for new vehicle floor plan facilities, for continuing operations and discontinued operations 1.57%sah_WeightedAverageInterestRateNewVehicleFloorPlan 1.86%sah_WeightedAverageInterestRateNewVehicleFloorPlan 2.02%sah_WeightedAverageInterestRateNewVehicleFloorPlan
Amount recognized as reduction in cost of sales for continuing and discontinued operations $ 39.7sah_FloorPlanAssistanceRecognized $ 37.9sah_FloorPlanAssistanceRecognized $ 33.0sah_FloorPlanAssistanceRecognized
Average interest rate for used vehicle floor plan facilities, for continuing operations and discontinued operations 1.80%sah_WeightedAverageInterestRateUsedVehicleFloorPlan 2.78%sah_WeightedAverageInterestRateUsedVehicleFloorPlan 2.80%sah_WeightedAverageInterestRateUsedVehicleFloorPlan