Financing Receivables: (Details) (USD $) In Millions, unless otherwise specified						9 Months Ended				9 Months Ended				9 Months Ended				9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2011	Sep. 30, 2013 Net investment in sales-type and direct financing leases	Dec. 31, 2012 Net investment in sales-type and direct financing leases	Sep. 30, 2013 Net investment in sales-type and direct financing leases Financing receivable, lower range of payment terms	Sep. 30, 2013 Net investment in sales-type and direct financing leases Financing receivable, upper range of payment terms	Sep. 30, 2013 Commercial financing receivables	Dec. 31, 2012 Commercial financing receivables	Sep. 30, 2013 Commercial financing receivables Financing receivable, lower range of payment terms	Sep. 30, 2013 Commercial financing receivables Financing receivable, upper range of payment terms	Sep. 30, 2013 Client loan receivables	Dec. 31, 2012 Client loan receivables	Sep. 30, 2013 Client loan receivables Financing receivable, lower range of payment terms	Sep. 30, 2013 Client loan receivables Financing receivable, upper range of payment terms	Sep. 30, 2013 Installment payment receivables	Dec. 31, 2012 Installment payment receivables	Sep. 30, 2013 Installment payment receivables Financing receivable, lower range of payment terms	Sep. 30, 2013 Installment payment receivables Financing receivable, upper range of payment terms
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivables used as collateral for non-recourse borrowings	$ 701	$ 650
Financing receivables held for sale	0	0
Financing receivables, current
Financing receivables, net, current	16,786	18,038		4,078	3,862			6,278	7,750			5,218	5,395			1,212	1,031
Financing receivables, noncurrent
Financing receivables, net, noncurrent	11,675	12,812		5,454	6,107				5			5,555	5,966			666	733
Financing receivables
Financing receivable, payment terms						2 years	6 years			30 days	90 days			1 year	7 years			1 year	3 years
Sales-type and direct financing leases, unguaranteed residual value				734	794
Sales-type and direct financing leases, unearned income				676	728
Allowance for credit losses	$ 324	$ 318	$ 307	$ 106	$ 114			$ 27	$ 46			$ 182	$ 155			$ 36	$ 39