This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for less than twelve months.

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- Definition

The amount of other than temporary impairment losses on investments in debt and equity securities categorized as Available-for-sale which have been recognized in earnings during the period. Such impairment losses consist of other than temporary impairments (OTTI) on equity securities, credit losses on investments in debt securities, and when the entity intends to sell an impaired debt security or it is more likely than not that the entity will be required to sell the impaired debt security before recovery of its amortized cost basis.

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Investments in Marketable Securities (Realized and Unrealized Losses) (Details) (USD $) In Millions, unless otherwise specified																	3 Months Ended
	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2013 Corporate debt securities [Member] Debt instruments [Member]	Mar. 31, 2013 Corporate debt securities [Member] Debt instruments [Member]	Jun. 30, 2013 U.S. government and agency obligations [Member] Debt instruments [Member]	Mar. 31, 2013 U.S. government and agency obligations [Member] Debt instruments [Member]	Jun. 30, 2013 U.S. government agency mortgage-backed securities [Member] Debt instruments [Member]	Mar. 31, 2013 U.S. government agency mortgage-backed securities [Member] Debt instruments [Member]	Jun. 30, 2013 U.S. government sector fund [Member] Equity instruments [Member]	Mar. 31, 2013 U.S. government sector fund [Member] Equity instruments [Member]	Jun. 30, 2013 Short-term sector fund [Member] Equity instruments [Member]	Mar. 31, 2013 Short-term sector fund [Member] Equity instruments [Member]	Jun. 30, 2013 Real return sector fund [Member] Equity instruments [Member]	Mar. 31, 2013 Real return sector fund [Member] Equity instruments [Member]	Jun. 30, 2013 International sector fund [Member] Equity instruments [Member]	Mar. 31, 2013 International sector fund [Member] Equity instruments [Member]	Jun. 30, 2013 Mortgage sector fund [Member]	Jun. 30, 2012 Mortgage sector fund [Member]	Jun. 30, 2013 Mortgage sector fund [Member] Equity instruments [Member]	Mar. 31, 2013 Mortgage sector fund [Member] Equity instruments [Member]	Jun. 30, 2013 Non-agency commercial mortgage-backed securities [Member] Debt instruments [Member]	Jun. 30, 2013 Emerging market sector fund [Member] Equity instruments [Member]	Mar. 31, 2013 Emerging market sector fund [Member] Equity instruments [Member]
OTTI losses recognized in income
Impairment write-downs																	$ 30	$ 0
Aging of fair value and gross unrealized losses for AFS securities
Less than 12 months, fair value	836	532	93	0	35	0	38	0	319	0		0	270	0	0	0			0	532	29	52	0
12 months or more, fair value	0	116
Less than 12 months, unrealized losses	(31)	(12)	(4)	0	(1)	0	(1)	0	(5)	0	0	0	(16)	0	0	0			0	(12)	(2)	(2)	0
12 months or more, unrealized losses	$ 0	$ 3