Cat Financial Financing Activities (Details 3) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Allowance for Credit Losses
Ending Balance - individually evaluated for impairment	$ 54	$ 56
Ending Balance - collectively evaluated for impairment	322	310
Ending Balance - Recorded Investment in Finance Receivables	376	366	362
Recorded Investment in Finance Receivables:
Ending Balance - individually evaluated for impairment	589	575
Ending Balance - collectively evaluated for impairment	20,146	19,405
Ending Balance - recorded investment in finance receivables	20,735	19,980
North America
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	7,257	7,291
Europe
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	2,363	2,281
Asia Pacific
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	3,076	3,038
Mining
Allowance for Credit Losses
Ending Balance - Recorded Investment in Finance Receivables	1,673	1,485
Latin America
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	3,236	2,965
Global Power Finance
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	3,130	2,920
Performing
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	20,212	19,508
Performing | North America
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	7,154	7,179
Performing | Europe
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	2,307	2,223
Performing | Asia Pacific
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	3,043	3,014
Performing | Mining
Allowance for Credit Losses
Ending Balance - Recorded Investment in Finance Receivables	1,661	1,473
Performing | Latin America
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	3,074	2,857
Performing | Global Power Finance
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	2,973	2,762
Non-Performing
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	523	472
Non-Performing | North America
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	103	112
Non-Performing | Europe
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	56	58
Non-Performing | Asia Pacific
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	33	24
Non-Performing | Mining
Allowance for Credit Losses
Ending Balance - Recorded Investment in Finance Receivables	12	12
Non-Performing | Latin America
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	162	108
Non-Performing | Global Power Finance
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	157	158
Customer
Allowance for Credit Losses
Ending Balance - individually evaluated for impairment	54	56
Ending Balance - collectively evaluated for impairment	315	304
Ending Balance - Recorded Investment in Finance Receivables	369	360	357
Recorded Investment in Finance Receivables:
Ending Balance - individually evaluated for impairment	589	575
Ending Balance - collectively evaluated for impairment	17,619	17,018
Ending Balance - recorded investment in finance receivables	18,208	17,593
Customer | North America
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	5,548	5,602
Customer | Europe
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	2,307	2,224
Customer | Asia Pacific
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	2,896	2,877
Customer | Mining
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	1,672	1,485
Customer | Latin America
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	2,655	2,485
Customer | Global Power Finance
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	3,130	2,920
Customer | Performing
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	17,685	17,121
Customer | Performing | North America
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	5,445	5,490
Customer | Performing | Europe
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	2,251	2,166
Customer | Performing | Asia Pacific
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	2,863	2,853
Customer | Performing | Mining
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	1,660	1,473
Customer | Performing | Latin America
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	2,493	2,377
Customer | Performing | Global Power Finance
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	2,973	2,762
Customer | Non-Performing
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	523	472
Customer | Non-Performing | North America
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	103	112
Customer | Non-Performing | Europe
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	56	58
Customer | Non-Performing | Asia Pacific
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	33	24
Customer | Non-Performing | Mining
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	12	12
Customer | Non-Performing | Latin America
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	162	108
Customer | Non-Performing | Global Power Finance
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	157	158
Dealer
Allowance for Credit Losses
Ending Balance - collectively evaluated for impairment	7	6
Ending Balance - Recorded Investment in Finance Receivables	7	6	5
Recorded Investment in Finance Receivables:
Ending Balance - collectively evaluated for impairment	2,527	2,387
Ending Balance - recorded investment in finance receivables	2,527	2,387
Dealer | North America
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	1,709	1,689
Dealer | Europe
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	56	57
Dealer | Asia Pacific
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	180	161
Dealer | Mining
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	1
Dealer | Latin America
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	581	480
Dealer | Performing
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	2,527	2,387
Dealer | Performing | North America
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	1,709	1,689
Dealer | Performing | Europe
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	56	57
Dealer | Performing | Asia Pacific
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	180	161
Dealer | Performing | Mining
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	1
Dealer | Performing | Latin America
Recorded Investment in Finance Receivables:
Ending Balance - recorded investment in finance receivables	$ 581	$ 480