Changes in Accumulated Other Comprehensive (Loss) Income (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Changes in Other Comprehensive income
Balances as of start of period	$ (2,428)
Net unrealized Pension and other postretirement benefits, net of tax	28	$ (8)
Balances as of end of period	(2,381)
Tax impact for the changes in each component of accumulated other comprehensive (loss) income
Investment securities	(3)	3
Foreign currency translation adjustments	2	(191)
Net investment hedges	(54)	(140)
Pension and other postretirement benefits	3	(9)
Total tax impact	(52)	(337)
Accumulated Other Comprehensive Loss [Member]
Changes in Other Comprehensive income
Balances as of start of period	(2,428)	(2,784)
Net unrealized gains	(13)	6
Increase (decrease) due to amounts reclassified into earnings	0	0
Net translation gain of investments in foreign operations	192	545
Net losses related to hedges of investment in foreign operations	(162)	(229)
Net unrealized Pension and other postretirement benefits, net of tax	28	(8)
Net change in accumulated other comprehensive income (loss)	47	314
Other - Net Unrealized Gains (Losses) on Equity Securities	2
Balances as of end of period	(2,381)	(2,470)
Net Unrealized Gains (Losses) on Investment Securities [Member]
Changes in Other Comprehensive income
Balances as of start of period	0	7
Net unrealized gains	(13)	6
Increase (decrease) due to amounts reclassified into earnings	0	0
Net translation gain of investments in foreign operations	0	0
Net losses related to hedges of investment in foreign operations	0	0
Net unrealized Pension and other postretirement benefits, net of tax	0	0
Net change in accumulated other comprehensive income (loss)	(11)	6
Other - Net Unrealized Gains (Losses) on Equity Securities	2
Balances as of end of period	(11)	13
Foreign Currency Translation Adjustments [Member]
Changes in Other Comprehensive income
Balances as of start of period	(1,961)	(2,262)
Net unrealized gains	0	0
Increase (decrease) due to amounts reclassified into earnings	0	0
Net translation gain of investments in foreign operations	192	545
Net losses related to hedges of investment in foreign operations	(162)	(229)
Net unrealized Pension and other postretirement benefits, net of tax	0	0
Net change in accumulated other comprehensive income (loss)	30	316
Other - Net Unrealized Gains (Losses) on Equity Securities	0
Balances as of end of period	(1,931)	(1,946)
Net Unrealized Pension and Other Postretirement Gains (Losses) [Member]
Changes in Other Comprehensive income
Balances as of start of period	(467)	(529)
Net unrealized gains	0	0
Increase (decrease) due to amounts reclassified into earnings	0	0
Net translation gain of investments in foreign operations	0	0
Net losses related to hedges of investment in foreign operations	0	0
Net unrealized Pension and other postretirement benefits, net of tax	28	(8)
Net change in accumulated other comprehensive income (loss)	28	(8)
Other - Net Unrealized Gains (Losses) on Equity Securities	0
Balances as of end of period	$ (439)	$ (537)