Segment Reporting (Schedule Of Revenue And (Loss) Income Before Taxes by Segment) (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Segment Reporting [Line Items]
Revenues	$ 284,249,000	$ 58,210,000	$ 369,795,000	$ 119,582,000	$ 317,960,000	$ 73,060,000	$ 281,410,000	$ 101,879,000	$ 831,836,000	$ 774,309,000	$ 484,958,000
Investment Income, Interest									4,002,000	1,739,000	5,357,000
Interest Expense									41,498,000	46,819,000	45,708,000
Depreciation, Depletion and Amortization, Nonproduction									17,604,000	16,492,000	21,560,000
Segment (loss) income before taxes									231,389,000	225,579,000	15,395,000
Short-term interest-free advance maturity term									6
Auction [Member]
Segment Reporting [Line Items]
Revenues									791,738,000	731,021,000	448,768,000
Investment Income, Interest									4,622,000	2,217,000	5,952,000
Interest Expense									41,492,000	46,814,000	45,616,000
Depreciation, Depletion and Amortization, Nonproduction									17,228,000	15,605,000	18,594,000
Segment (loss) income before taxes									225,600,000	217,227,000	15,427,000
Finance [Member]
Segment Reporting [Line Items]
Revenues									16,265,000	17,200,000	12,671,000
Investment Income, Interest
Interest Expense
Depreciation, Depletion and Amortization, Nonproduction									113,000	101,000	140,000
Segment (loss) income before taxes									12,110,000	14,776,000	7,244,000
Non-operating gain related to the remeasurement of a foreign currency									1,000,000	3,400,000	(2,000,000)
Dealer [Member]
Segment Reporting [Line Items]
Revenues									21,790,000	29,092,000	22,339,000
Investment Income, Interest
Interest Expense									6,000	5,000	92,000
Depreciation, Depletion and Amortization, Nonproduction									231,000	757,000	2,810,000
Segment (loss) income before taxes									(9,289,000)	(1,697,000)	(10,359,000)
All Other [Member]
Segment Reporting [Line Items]
Revenues									6,270,000	4,511,000	4,778,000
Investment Income, Interest											1,000
Interest Expense										0
Depreciation, Depletion and Amortization, Nonproduction									32,000	29,000	16,000
Segment (loss) income before taxes									4,604,000	2,737,000	2,413,000
Reconciling Items [Member]
Segment Reporting [Line Items]
Revenues									(4,227,000)	(7,515,000)	(3,598,000)
Investment Income, Interest									(620,000)	(478,000)	(596,000)
Interest Expense
Depreciation, Depletion and Amortization, Nonproduction
Segment (loss) income before taxes									$ (1,636,000)	$ (7,464,000)	$ 670,000
Short-term interest-free advance maturity term									3