Changes in Accumulated Other Comprehensive (Loss) Income (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Changes in Other Comprehensive income
Balances as of start of period	$ (1,426)
Pension and other postretirement benefit losses	27	27
Balances as of end of period	(1,394)
Accumulated Other Comprehensive (Loss) Income [Member]
Changes in Other Comprehensive income
Balances as of start of period	(1,426)	(927)
Net unrealized gains / (losses)	68	(12)
Reclassification for realized (gains) / losses into earnings	(28)	(23)
Net translation of investments in foreign operations	(18)	11
Net losses related to hedges of investment in foreign operations	(17)	(56)
Pension and other postretirement benefit losses	27	27
Net change in accumulated other comprehensive (loss) income	32	(53)
Balances as of end of period	(1,394)	(980)
Net Unrealized Investment Gains (Losses) on Investment Securities [Member]
Changes in Other Comprehensive income
Balances as of start of period	63	315
Net unrealized gains / (losses)	68	(12)
Reclassification for realized (gains) / losses into earnings	(29)	(23)
Net change in accumulated other comprehensive (loss) income	39	(35)
Balances as of end of period	102	280
Foreign Currency Translation Adjustments [Member]
Changes in Other Comprehensive income
Balances as of start of period	(1,090)	(754)
Reclassification for realized (gains) / losses into earnings	1
Net translation of investments in foreign operations	(18)	11
Net losses related to hedges of investment in foreign operations	(17)	(56)
Net change in accumulated other comprehensive (loss) income	(34)	(45)
Balances as of end of period	(1,124)	(799)
Net Unrealized Pension and Other Postretirement Benefit Losses [Member]
Changes in Other Comprehensive income
Balances as of start of period	(399)	(488)
Pension and other postretirement benefit losses	27	27
Net change in accumulated other comprehensive (loss) income	27	27
Balances as of end of period	$ (372)	$ (461)