Equity Method Investees (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended										3 Months Ended		12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Jacobs Group	Dec. 31, 2012 The Nix Group	Dec. 31, 2012 Penske Wynn Ferrari Maserati	Dec. 31, 2012 Max Cycles	Dec. 31, 2012 Innovative Media	Dec. 31, 2012 QEK Global Solutions	Dec. 31, 2012 Fleetwash, LLC	Dec. 31, 2010 National Powersport Auctions	Dec. 31, 2012 National Powersport Auctions	Dec. 31, 2012 Penske Truck Leasing Co., L.P. ("PTL")	Dec. 31, 2011 Penske Truck Leasing Co., L.P. ("PTL")	Dec. 31, 2012 Jacobs Group, The Nix Group, Penske Wynn Ferrari Maserati, Max Cycles, Innovative Media,QEK Global Solutions and Fleetwash, LLC equity method investment	Dec. 31, 2011 Jacobs Group, The Nix Group, Penske Wynn Ferrari Maserati, Max Cycles, Innovative Media,QEK Global Solutions and Fleetwash, LLC equity method investment
Equity Method Investment
Ownership percentage of Equity Method Investment				50.00%	50.00%	50.00%	50.00%	45.00%	22.50%	7.00%		7.00%
Equity Method Investment sold											$ 14,616
Pre tax gain on sale of investment											5,295
Equity method investments	303,160	298,640											242,791	240,254	60,369	58,386
Limited partnership interest (as a percent)													9.00%
Condensed income statement information
Revenues	6,043,432	5,970,595	4,531,588
Gross margin	1,897,310	1,802,301	1,749,504
Net income	284,228	255,145	198,793
Equity in net income of affiliates	27,572	25,451	20,569
Condensed balance sheet information
Current assets	1,129,698	1,159,066
Noncurrent assets	8,139,122	7,228,052
Total assets	9,268,820	8,387,118
Current liabilities	866,219	916,344
Noncurrent liabilities	6,475,453	6,330,666
Equity	1,927,148	1,140,108
Total liabilities and equity	$ 9,268,820	$ 8,387,118