Financing Receivables: (Details 2) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013 Major Markets	Dec. 31, 2012 Major Markets	Sep. 30, 2013 Growth Markets	Dec. 31, 2012 Growth Markets	Sep. 30, 2013 Lease receivables	Dec. 31, 2012 Lease receivables	Dec. 31, 2011 Lease receivables	Sep. 30, 2013 Lease receivables Major Markets	Dec. 31, 2012 Lease receivables Major Markets	Dec. 31, 2011 Lease receivables Major Markets	Sep. 30, 2013 Lease receivables Growth Markets	Dec. 31, 2012 Lease receivables Growth Markets	Dec. 31, 2011 Lease receivables Growth Markets	Sep. 30, 2013 Loan receivables	Dec. 31, 2012 Loan receivables	Dec. 31, 2011 Loan receivables	Sep. 30, 2013 Loan receivables Major Markets	Dec. 31, 2012 Loan receivables Major Markets	Dec. 31, 2011 Loan receivables Major Markets	Sep. 30, 2013 Loan receivables Growth Markets	Dec. 31, 2012 Loan receivables Growth Markets	Dec. 31, 2011 Loan receivables Growth Markets
Financing Receivables
Ending Balance	$ 21,681	$ 22,510	$ 15,747	$ 16,701	$ 5,934	$ 5,808	$ 8,809	$ 9,174		$ 6,705	$ 7,036		$ 2,104	$ 2,138		$ 12,871	$ 13,336		$ 9,042	$ 9,666		$ 3,830	$ 3,670
Collectively evaluated for impairment	21,395	22,254	15,629	16,570	5,767	5,684
Individually evaluated for impairment	285	256	118	131	167	125
Allowance for Credit Losses
Allowance for credit losses, beginning balance	318	307	180	203	138	104	106	114	118	42	59	79	64	55	40	218	204	189	92	121	125	126	84	64
Write-offs	(30)	(15)	(21)	(14)	(9)	(1)
Provision	40	28	(26)	(9)	66	38
Other	(4)	(2)		0	(4)	(2)
Allowance for credit losses, ending balance	324	318	134	180	190	138	106	114	118	42	59	79	64	55	40	218	204	189	92	121	125	126	84	64
Collectively evaluated for impairment	77	98	40	69	37	29
Individually evaluated for impairment	$ 247	$ 220	$ 94	$ 111	$ 153	$ 109