Fair Value of Financial Instruments - Estimated Incremental Borrowing Rates for Similar Types of Borrowing Arrangements (Detail) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Level 3 [Member] | Carrying Amount [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Manufacturer flooring plans payable with interest computed at 3.5% (Level 3)	$ 17,543	$ 9,615
Level 3 [Member] | Fair Value [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Manufacturer flooring plans payable with interest computed at 3.5% (Level 3)	15,823	8,976
Level 2 [Member] | Carrying Amount [Member] | Senior Unsecured Notes Due 2028 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Senior unsecured notes due 2028 with interest computed at 3.875% (Level 2)	1,239,606	1,238,660
Level 2 [Member] | Fair Value [Member] | Senior Unsecured Notes Due 2028 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Senior unsecured notes due 2028 with interest computed at 3.875% (Level 2)	$ 1,247,975	$ 1,259,413