AOCI Rollforward (Details 2) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		$ 229	$ 200
OCI before reclassifications		(229)	25
Amounts reclassified from AOCI		(4)	(6)
Total other comprehensive income (loss), net of tax		(233)	19
Ending balance		(5)	219
Noncredit related impairments on securities and net unrealized securities gains (losses) on previously impaired securities		0	8
Net unrealized securities gains (losses) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		486	479
OCI before reclassifications		(258)	19
Amounts reclassified from AOCI		(4)	(12)
Total other comprehensive income (loss), net of tax		(262)	7
Ending balance	[1]	223	486
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total other comprehensive income (loss), net of tax		(233)	19
Net unrealized derivatives gains (losses) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		8	5
OCI before reclassifications		0	0
Amounts reclassified from AOCI		0	1
Total other comprehensive income (loss), net of tax		0	1
Ending balance		8	6
Defined benefit plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(97)	(125)
OCI before reclassifications		0	0
Amounts reclassified from AOCI		0	5
Total other comprehensive income (loss), net of tax		0	5
Ending balance		(97)	(120)
Foreign currency translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(167)	(159)
OCI before reclassifications		29	7
Amounts reclassified from AOCI		0	0
Total other comprehensive income (loss), net of tax		29	7
Ending balance		(138)	(152)
Other [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(1)	0
OCI before reclassifications		0	(1)
Amounts reclassified from AOCI		0	0
Total other comprehensive income (loss), net of tax		0	(1)
Ending balance	[1]	(1)	$ (1)
Cumulative effect of change in accounting policies - Recognition and measurement of financial instruments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative effect of change in accounting policies		0
Cumulative effect of change in accounting policies - Recognition and measurement of financial instruments | Net unrealized securities gains (losses) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative effect of change in accounting policies		(1)
Cumulative effect of change in accounting policies - Recognition and measurement of financial instruments | AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative effect of change in accounting policies		$ (1)

[1] Includes nil and $8 million of noncredit related impairments on securities and net unrealized securities gains (losses) on previously impaired securities as of March 31, 2018 and March 31, 2017, respectively.