Financial Instruments: (Details 4) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Derivative instruments in fair value hedging relationships | Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	$ 4,500,000,000	$ 4,300,000,000
Average remaining maturity	7 years 6 months	5 years 1 month
Derivative instruments in cash flow hedging relationships | Foreign exchange forward contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	10,700,000,000	10,700,000,000
Average remaining maturity	8 months	8 months
Net gains (losses) before taxes in other comprehensive income/(loss), cash flow hedges of borrowings	(326,000,000)	(138,000,000)
Gains (losses) expected to be reclassified to net income within the next 12 months	(197,000,000)	(79,000,000)
Maximum length of time hedged	4 years
Derivative instruments in cash flow hedging relationships | Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Net gains (losses) before taxes in other comprehensive income/(loss), cash flow hedges of borrowings	1,000,000	1,000,000
Gains (losses) expected to be reclassified to net income within the next 12 months	1,000,000	1,000,000
Derivative instruments in net investment hedging relationships
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	5,300,000,000	3,300,000,000
Average remaining maturity	2 months 12 days	4 months 24 days
Derivative instruments not designated as hedging instruments | Foreign exchange forward and swap contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	14,600,000,000	12,900,000,000
Maximum length of time hedged	1 year
Derivative instruments not designated as hedging instruments | Equity contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional amount	$ 1,200,000,000	$ 1,200,000,000