Debt and Capital Lease Obligations (Details) (USD $)			9 Months Ended			9 Months Ended				3 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended			9 Months Ended		9 Months Ended				9 Months Ended							9 Months Ended				9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 Revolving Credit Facility [Member]	Dec. 31, 2011 Revolving Credit Facility [Member]	Sep. 30, 2012 Revolving Credit Facility [Member] Consortium of Banks [Member]	Sep. 30, 2012 Revolving Credit Facility [Member] CAI Rail Inc [Member]	Dec. 31, 2011 Revolving Credit Facility [Member] CAI Rail Inc [Member]	Sep. 30, 2012 Revolving Credit Facility [Member] CAI Rail Inc [Member] Maximum [Member]	Sep. 30, 2012 Revolving Credit Facility [Member] CAI Rail Inc [Member] Minimum [Member]	Mar. 31, 2012 Asset-Backed Warehouse Notes [Member]	Sep. 30, 2012 Asset-Backed Warehouse Notes [Member]	Dec. 31, 2011 Asset-Backed Warehouse Notes [Member]	Sep. 30, 2012 Term Loan [Member] Consortium of Banks [Member]	Dec. 31, 2011 Term Loan [Member] Consortium of Banks [Member]	Dec. 31, 2010 Term Loan [Member] Consortium of Banks [Member]	Sep. 30, 2012 Term Loan [Member] Consortium of banks, note dated April 11, 2012 [Member]	Dec. 31, 2011 Term Loan [Member] Consortium of banks, note dated April 11, 2012 [Member]	Sep. 30, 2012 Term Loan [Member] Development Bank of Japan [Member]	Dec. 31, 2011 Term Loan [Member] Development Bank of Japan [Member]	Sep. 30, 2012 Term Loan [Member] Federal Funds Rate [Member] Consortium of Banks [Member]	Sep. 30, 2012 Term Loan [Member] Eurodollar Rate [Member] Consortium of Banks [Member]	Sep. 30, 2012 Capital Lease Obligations [Member]	Sep. 30, 2012 Capital Lease Obligations [Member] Maximum [Member]	Sep. 30, 2012 Capital Lease Obligations [Member] Minimum [Member]	Sep. 30, 2012 Senior Secured Notes [Member]	Dec. 31, 2011 Senior Secured Notes [Member]	Sep. 30, 2012 Letter of Credit [Member]	Sep. 30, 2012 Letter of Credit [Member] Consortium of Banks [Member]	Sep. 30, 2012 Swing Line Loans [Member]	Sep. 30, 2012 Swing Line Loans [Member] Consortium of Banks [Member]	Sep. 30, 2012 Collateralized Financing Obligation [Member]	Dec. 31, 2011 Collateralized Financing Obligation [Member]	Sep. 30, 2012 Collateralized Financing Obligation [Member] Maximum [Member]	Sep. 30, 2012 Collateralized Financing Obligation [Member] Minimum [Member]
Debt Instrument [Line Items]
Current Outstanding	$ 39,387,000	$ 25,764,000	$ 0	$ 0		$ 0	$ 0				$ 0	$ 0	$ 24,964,000	$ 24,964,000		$ 5,383,000	$ 0	$ 800,000	$ 800,000						$ 8,240,000	$ 0					$ 0	$ 0
Long-term Outstanding	825,687,000	575,014,000	321,000,000	261,000,000		39,269,000	0				0	51,000,000	236,891,000	255,614,000		73,567,000	0	6,800,000	7,400,000						94,760,000	0					53,400,000	0
Average Interest Rate (in hundredths)			3.00%	3.00%		2.50%	0.00%				0.00%	2.80%	3.40%	3.50%		2.70%	0.00%	2.80%	2.80%						4.90%	0.00%					1.10%	0.00%
Agreement Terminates			Sep. 30, 2014			Jun. 30, 2015					Sep. 30, 2023		Dec. 20, 2016			Apr. 11, 2017		Jul. 31, 2014					Jun. 30, 2019	Oct. 31, 2012	Sep. 13, 2022								Nov. 30, 2016	Jun. 30, 2014
Maximum credit commitment					495,000,000	85,000,000																						15,000,000		10,000,000
Maximum amount credit facility might be increased			675,000,000													200,000,000
Number of business days in which short term borrowings are payable (in days)																													10 days
Availability under the revolving credit facility			173,900,000			45,700,000																					100,000
Variable interest rate (in hundredths)								2.25%	1.50%
Term loans													300,000,000			80,000,000		10,000,000
Number of quarterly installments													23					19
Quarterly payments of principal													3,700,000					200,000
Initiation date of loan agreement																		Oct. 31, 2009
Debt instrument final payment													99,900,000					6,200,000
Amount outstanding under the facility													261,900,000			79,000,000		7,600,000							103,000,000						53,400,000
Principal amount of loan											100,000,000				185,000,000	60,000,000									103,000,000
Term of Debt Instrument													6 years			5 years		5 years
Periodic payments specified as percentage of drawn amount (in hundredths)													2.00%			1.75%
Debt instrument final payment in percentage (in hundredths)													54.00%
Numerator for calculation of quarterly payments of principal specified in percentage (in hundredths)													46.00%
Basis spread on variable rate (in hundredths)																2.50%				0.05%	1.00%
Percentage of aggregate principal to prepay, minimum (in hundredths)																									10.00%
Proceeds Used to Repay Credit Facility																									100,000,000
Proceeds Used for Working Capital Purposes																													3,000,000
Proceeds from the facility										49,000,000		51,000,000
Capital Lease Obligations [Abstract]
Capital lease obligations	$ 8,000,000																					$ 8,000,000
Average interest rate on capital lease obligations (in hundredths)																						3.00%