Shareholders' Equity AOCI Rollforward (Details 2) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		$ 200		$ 253		$ 662
OCI before reclassifications		54		(54)		(411)
Amounts reclassified from AOCI		(25)		(5)		2
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent		29		(59)		(409)
Ending balance		229		200		253
Net unrealized securities gains [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		479	[1]	426	[1]	786
Cumulative Effect of New Accounting Principle in Period of Adoption						6
OCI before reclassifications		43		61		(356)
Amounts reclassified from AOCI		(36)		(14)		(4)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent		7		47		(360)
Ending balance	[1]	486		479		426
Noncredit related impairments on AFS securities		1		4		4
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption						6
Net unrealized derivatives losses [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		5		1		0
Amounts reclassified from AOCI		3		4		1
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent		3		4		1
Ending balance		8		5		1
Defined benefit plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(125)		(91)		(71)
OCI before reclassifications		20		(39)		(25)
Amounts reclassified from AOCI		8		5		5
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent		28		(34)		(20)
Ending balance		(97)		(125)		(91)
Foreign currency translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		(159)		(83)		(53)
OCI before reclassifications		(8)		(76)		(30)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent		(8)		(76)		(30)
Ending balance		(167)		(159)		(83)
Accumulated Net Unrealized From Other Investment Gain Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		0		0		0
OCI before reclassifications		(1)		0		0
Amounts reclassified from AOCI		0		0		0
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent		(1)		0		0
Ending balance		$ (1)		$ 0		$ 0

[1] Includes $1 million, $4 million and $4 million of noncredit related impairments on securities and net unrealized securities gains (losses) on previously impaired securities at December 31, 2017, 2016 and 2015, respectively.