The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Topic 230
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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The cumulative amount of credit losses recognized in earnings related to debt securities held for which a portion of an other than temporary impairment (OTTI) was recognized in other comprehensive income (a component of shareholders' equity).

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Investment Holding Level 4 Other-Than-Temporary Impairment Losses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Held-to-maturity Securities	$ 13	$ 5	$ 14	$ 23
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Available-for-sale Securities	14	7	15	30
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net	14	7	15	30
Other than Temporary Impairment Losses, Investments	14	7	15	30
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Roll Forward]
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Credit Losses on Debt Securities Held	236	293	236	293	$ 260	$ 280	$ 336	$ 324
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Additions, No Previous Impairment	0	4	1	21
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Additions, Additional Credit Losses	13	1	13	2
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Reductions, Securities Sold	29	35	41	36
Other than Temporary Impairment, Credit Losses Recognized in Earnings, Reductions, Cash Flows	8	13	17	18
Available-for-sale Securities [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Available-for-sale Securities	0	1	0	3
Equity Securities [Member]
Other than Temporary Impairment, Credit Losses Recognized in Earnings [Line Items]
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net	$ 1	$ 1	$ 1	$ 4