Financial Instruments: (Details 4) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Derivative instruments in fair value hedging relationships | Interest rate swaps
Derivative Instruments, Gain (Loss)
Notional amount	$ 5,900	$ 3,100
Average remaining maturity	9 years 6 months	10 years 7 months
Derivative instruments in cash flow hedging relationships | Foreign exchange forward contracts
Derivative Instruments, Gain (Loss)
Notional amount	10,200	10,200
Average remaining maturity	8 months	8 months
Net gains (losses) before taxes in other comprehensive income/(loss), cash flow hedges of borrowings	(169)	(252)
Gains (losses) expected to be reclassified to net income within the next 12 months	(155)	(166)
Maximum length of time hedged	4 years
Derivative instruments in cash flow hedging relationships | Interest rate swaps
Derivative Instruments, Gain (Loss)
Net gains (losses) before taxes in other comprehensive income/(loss), cash flow hedges of borrowings	1	1
Gains (losses) expected to be reclassified to net income within the next 12 months	1	1
Derivative instruments in cash flow hedging relationships | Currency swaps
Derivative Instruments, Gain (Loss)
Notional amount	1,200	1,200
Net gains (losses) before taxes in other comprehensive income/(loss), cash flow hedges of borrowings	(6)	(9)
Gains (losses) expected to be reclassified to net income within the next 12 months	(3)	(3)
Maximum length of time hedged	7 years
Derivative instruments in net investment hedging relationships
Derivative Instruments, Gain (Loss)
Notional amount	3,400	3,000
Average remaining maturity	4 months 24 days	4 months 24 days
Derivative instruments not designated as hedging instruments | Foreign exchange forward and swap contracts
Derivative Instruments, Gain (Loss)
Notional amount	16,300	14,700
Maximum length of time hedged	1 year
Derivative instruments not designated as hedging instruments | Equity contracts
Derivative Instruments, Gain (Loss)
Notional amount	$ 1,200	$ 1,300