Fair Value Measurements (Financial Assets and Liabilities Measured at Fair Value On a Recurring Basis) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Jun. 30, 2012 U.S. government and agency obligations [Member]	Sep. 30, 2012 Recurring [Member]	Mar. 31, 2012 Recurring [Member]	Sep. 30, 2012 Recurring [Member] Foreign currency swaps [Member]	Mar. 31, 2012 Recurring [Member] Foreign currency swaps [Member]	Sep. 30, 2012 Recurring [Member] Interest rate cap [Member]	Mar. 31, 2012 Recurring [Member] Interest rate cap [Member]	Sep. 30, 2012 Recurring [Member] Interest rate swap [Member]	Mar. 31, 2012 Recurring [Member] Interest rate swap [Member]	Sep. 30, 2012 Recurring [Member] Debt instruments [Member] U.S. government and agency obligations [Member]	Mar. 31, 2012 Recurring [Member] Debt instruments [Member] U.S. government and agency obligations [Member]	Sep. 30, 2012 Recurring [Member] Debt instruments [Member] Municipal debt securities [Member]	Mar. 31, 2012 Recurring [Member] Debt instruments [Member] Municipal debt securities [Member]	Sep. 30, 2012 Recurring [Member] Debt instruments [Member] Foreign government debt securities [Member]	Mar. 31, 2012 Recurring [Member] Debt instruments [Member] Foreign government debt securities [Member]	Sep. 30, 2012 Recurring [Member] Debt instruments [Member] Corporate debt securities [Member]	Mar. 31, 2012 Recurring [Member] Debt instruments [Member] Corporate debt securities [Member]	Sep. 30, 2012 Recurring [Member] Debt instruments [Member] U.S. government agency mortgage-backed securities [Member]	Mar. 31, 2012 Recurring [Member] Debt instruments [Member] U.S. government agency mortgage-backed securities [Member]	Sep. 30, 2012 Recurring [Member] Debt instruments [Member] Non-agency residential mortgage-backed securities [Member]	Mar. 31, 2012 Recurring [Member] Debt instruments [Member] Non-agency residential mortgage-backed securities [Member]	Sep. 30, 2012 Recurring [Member] Debt instruments [Member] Non-agency commercial mortgage-backed securities [Member]	Mar. 31, 2012 Recurring [Member] Debt instruments [Member] Non-agency commercial mortgage-backed securities [Member]	Sep. 30, 2012 Recurring [Member] Debt instruments [Member] Asset-backed securities [Member]	Mar. 31, 2012 Recurring [Member] Debt instruments [Member] Asset-backed securities [Member]	Sep. 30, 2012 Recurring [Member] Equity instruments [Member] Fixed income short-term sector fund [Member]	Mar. 31, 2012 Recurring [Member] Equity instruments [Member] Fixed income short-term sector fund [Member]	Sep. 30, 2012 Recurring [Member] Equity instruments [Member] Fixed income U.S. government sector fund [Member]	Mar. 31, 2012 Recurring [Member] Equity instruments [Member] Fixed income U.S. government sector fund [Member]	Sep. 30, 2012 Recurring [Member] Equity instruments [Member] Fixed income municipal sector fund [Member]	Mar. 31, 2012 Recurring [Member] Equity instruments [Member] Fixed income municipal sector fund [Member]	Sep. 30, 2012 Recurring [Member] Equity instruments [Member] Fixed income investement grade corporate sector fund [Member]	Mar. 31, 2012 Recurring [Member] Equity instruments [Member] Fixed income investement grade corporate sector fund [Member]	Sep. 30, 2012 Recurring [Member] Equity instruments [Member] Fixed income high-yield sector fund [Member]	Mar. 31, 2012 Recurring [Member] Equity instruments [Member] Fixed income high-yield sector fund [Member]	Sep. 30, 2012 Recurring [Member] Equity instruments [Member] Fixed income real return sector fund [Member]	Mar. 31, 2012 Recurring [Member] Equity instruments [Member] Fixed income real return sector fund [Member]	Sep. 30, 2012 Recurring [Member] Equity instruments [Member] Fixed income mortgage sector fund [Member]	Mar. 31, 2012 Recurring [Member] Equity instruments [Member] Fixed income mortgage sector fund [Member]	Sep. 30, 2012 Recurring [Member] Equity instruments [Member] Fixed income asset-backed securities sector fund [Member]	Mar. 31, 2012 Recurring [Member] Equity instruments [Member] Fixed income asset-backed securities sector fund [Member]	Sep. 30, 2012 Recurring [Member] Equity instruments [Member] Fixed income emerging market sector fund [Member]	Mar. 31, 2012 Recurring [Member] Equity instruments [Member] Fixed income emerging market sector fund [Member]	Sep. 30, 2012 Recurring [Member] Equity instruments [Member] Fixed income international sector fund [Member]	Mar. 31, 2012 Recurring [Member] Equity instruments [Member] Fixed income international sector fund [Member]	Sep. 30, 2012 Recurring [Member] Equity instruments [Member] Equity mutual fund - S&P 500 index [Member]	Mar. 31, 2012 Recurring [Member] Equity instruments [Member] Equity mutual fund - S&P 500 index [Member]	Sep. 30, 2012 Recurring [Member] Money market instruments [Member]	Mar. 31, 2012 Recurring [Member] Money market instruments [Member]	Sep. 30, 2012 Recurring [Member] Certificates of deposit [Member]	Mar. 31, 2012 Recurring [Member] Certificates of deposit [Member]	Sep. 30, 2012 Recurring [Member] Certificates of deposit [Member] Debt instruments [Member]	Mar. 31, 2012 Recurring [Member] Certificates of deposit [Member] Debt instruments [Member]	Sep. 30, 2012 Recurring [Member] Commercial paper [Member]	Mar. 31, 2012 Recurring [Member] Commercial paper [Member]	Sep. 30, 2012 Recurring [Member] Commercial paper [Member] Debt instruments [Member]	Mar. 31, 2012 Recurring [Member] Commercial paper [Member] Debt instruments [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Foreign currency swaps [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Foreign currency swaps [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Interest rate cap [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Interest rate cap [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Interest rate swap [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Interest rate swap [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Debt instruments [Member] U.S. government and agency obligations [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Debt instruments [Member] U.S. government and agency obligations [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Debt instruments [Member] Municipal debt securities [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Debt instruments [Member] Municipal debt securities [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Debt instruments [Member] Foreign government debt securities [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Debt instruments [Member] Foreign government debt securities [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Debt instruments [Member] Corporate debt securities [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Debt instruments [Member] Corporate debt securities [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Debt instruments [Member] U.S. government agency mortgage-backed securities [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Debt instruments [Member] U.S. government agency mortgage-backed securities [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Debt instruments [Member] Non-agency residential mortgage-backed securities [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Debt instruments [Member] Non-agency residential mortgage-backed securities [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Debt instruments [Member] Non-agency commercial mortgage-backed securities [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Debt instruments [Member] Non-agency commercial mortgage-backed securities [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Debt instruments [Member] Asset-backed securities [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Debt instruments [Member] Asset-backed securities [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Equity instruments [Member] Fixed income short-term sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Equity instruments [Member] Fixed income short-term sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Equity instruments [Member] Fixed income U.S. government sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Equity instruments [Member] Fixed income U.S. government sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Equity instruments [Member] Fixed income municipal sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Equity instruments [Member] Fixed income municipal sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Equity instruments [Member] Fixed income investement grade corporate sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Equity instruments [Member] Fixed income investement grade corporate sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Equity instruments [Member] Fixed income high-yield sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Equity instruments [Member] Fixed income high-yield sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Equity instruments [Member] Fixed income real return sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Equity instruments [Member] Fixed income real return sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Equity instruments [Member] Fixed income mortgage sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Equity instruments [Member] Fixed income mortgage sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Equity instruments [Member] Fixed income asset-backed securities sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Equity instruments [Member] Fixed income asset-backed securities sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Equity instruments [Member] Fixed income emerging market sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Equity instruments [Member] Fixed income emerging market sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Equity instruments [Member] Fixed income international sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Equity instruments [Member] Fixed income international sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Equity instruments [Member] Equity mutual fund - S&P 500 index [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Equity instruments [Member] Equity mutual fund - S&P 500 index [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Money market instruments [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Money market instruments [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Certificates of deposit [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Certificates of deposit [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Certificates of deposit [Member] Debt instruments [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Certificates of deposit [Member] Debt instruments [Member] Commercial paper [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Commercial paper [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Commercial paper [Member]	Sep. 30, 2012 Recurring [Member] Level 1 [Member] Commercial paper [Member] Debt instruments [Member]	Mar. 31, 2012 Recurring [Member] Level 1 [Member] Commercial paper [Member] Debt instruments [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Foreign currency swaps [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Foreign currency swaps [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Interest rate cap [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Interest rate cap [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Interest rate swap [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Interest rate swap [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Debt instruments [Member] U.S. government and agency obligations [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Debt instruments [Member] U.S. government and agency obligations [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Debt instruments [Member] Municipal debt securities [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Debt instruments [Member] Municipal debt securities [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Debt instruments [Member] Certificates Of Deposit [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Debt instruments [Member] Foreign government debt securities [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Debt instruments [Member] Foreign government debt securities [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Debt instruments [Member] Corporate debt securities [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Debt instruments [Member] Corporate debt securities [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Debt instruments [Member] U.S. government agency mortgage-backed securities [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Debt instruments [Member] U.S. government agency mortgage-backed securities [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Debt instruments [Member] Non-agency residential mortgage-backed securities [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Debt instruments [Member] Non-agency residential mortgage-backed securities [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Debt instruments [Member] Non-agency commercial mortgage-backed securities [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Debt instruments [Member] Non-agency commercial mortgage-backed securities [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Debt instruments [Member] Asset-backed securities [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Debt instruments [Member] Asset-backed securities [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Equity instruments [Member] Fixed income short-term sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Equity instruments [Member] Fixed income short-term sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Equity instruments [Member] Fixed income U.S. government sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Equity instruments [Member] Fixed income U.S. government sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Equity instruments [Member] Fixed income municipal sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Equity instruments [Member] Fixed income municipal sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Equity instruments [Member] Fixed income investement grade corporate sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Equity instruments [Member] Fixed income investement grade corporate sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Equity instruments [Member] Fixed income high-yield sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Equity instruments [Member] Fixed income high-yield sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Equity instruments [Member] Fixed income real return sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Equity instruments [Member] Fixed income real return sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Equity instruments [Member] Fixed income mortgage sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Equity instruments [Member] Fixed income mortgage sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Equity instruments [Member] Fixed income asset-backed securities sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Equity instruments [Member] Fixed income asset-backed securities sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Equity instruments [Member] Fixed income emerging market sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Equity instruments [Member] Fixed income emerging market sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Equity instruments [Member] Fixed income international sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Equity instruments [Member] Fixed income international sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Equity instruments [Member] Equity mutual fund - S&P 500 index [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Equity instruments [Member] Equity mutual fund - S&P 500 index [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Money market instruments [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Money market instruments [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Certificates of deposit [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Certificates of deposit [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Certificates of deposit [Member] Debt instruments [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Commercial paper [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Commercial paper [Member]	Sep. 30, 2012 Recurring [Member] Level 2 [Member] Commercial paper [Member] Debt instruments [Member]	Mar. 31, 2012 Recurring [Member] Level 2 [Member] Commercial paper [Member] Debt instruments [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member] Foreign currency swaps [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Foreign currency swaps [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member] Interest rate cap [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Interest rate cap [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member] Interest rate swap [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Interest rate swap [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member] Debt instruments [Member] U.S. government and agency obligations [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Debt instruments [Member] U.S. government and agency obligations [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member] Debt instruments [Member] Municipal debt securities [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Debt instruments [Member] Municipal debt securities [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member] Debt instruments [Member] Foreign government debt securities [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Debt instruments [Member] Foreign government debt securities [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member] Debt instruments [Member] Corporate debt securities [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Debt instruments [Member] Corporate debt securities [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member] Debt instruments [Member] U.S. government agency mortgage-backed securities [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Debt instruments [Member] U.S. government agency mortgage-backed securities [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member] Debt instruments [Member] Non-agency residential mortgage-backed securities [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Debt instruments [Member] Non-agency residential mortgage-backed securities [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member] Debt instruments [Member] Non-agency commercial mortgage-backed securities [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Debt instruments [Member] Non-agency commercial mortgage-backed securities [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member] Debt instruments [Member] Asset-backed securities [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Debt instruments [Member] Asset-backed securities [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member] Equity instruments [Member] Fixed income short-term sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Equity instruments [Member] Fixed income short-term sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member] Equity instruments [Member] Fixed income U.S. government sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Equity instruments [Member] Fixed income U.S. government sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member] Equity instruments [Member] Fixed income municipal sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Equity instruments [Member] Fixed income municipal sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member] Equity instruments [Member] Fixed income investement grade corporate sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Equity instruments [Member] Fixed income investement grade corporate sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member] Equity instruments [Member] Fixed income high-yield sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Equity instruments [Member] Fixed income high-yield sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member] Equity instruments [Member] Fixed income real return sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Equity instruments [Member] Fixed income real return sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member] Equity instruments [Member] Fixed income mortgage sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Equity instruments [Member] Fixed income mortgage sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member] Equity instruments [Member] Fixed income asset-backed securities sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Equity instruments [Member] Fixed income asset-backed securities sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member] Equity instruments [Member] Fixed income emerging market sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Equity instruments [Member] Fixed income emerging market sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member] Equity instruments [Member] Fixed income international sector fund [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Equity instruments [Member] Fixed income international sector fund [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member] Equity instruments [Member] Equity mutual fund - S&P 500 index [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Equity instruments [Member] Equity mutual fund - S&P 500 index [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Money market instruments [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member] Certificates of deposit [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Certificates of deposit [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member] Certificates of deposit [Member] Debt instruments [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Certificates of deposit [Member] Debt instruments [Member] Commercial paper [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member] Commercial paper [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Commercial paper [Member]	Sep. 30, 2012 Recurring [Member] Level 3 [Member] Commercial paper [Member] Debt instruments [Member]	Mar. 31, 2012 Recurring [Member] Level 3 [Member] Commercial paper [Member] Debt instruments [Member]	Sep. 30, 2012 Recurring [Member] Counterparty Netting & Collateral [Member]	Mar. 31, 2012 Recurring [Member] Counterparty Netting & Collateral [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents			$ 4,687	$ 4,879																																													$ 2,635	$ 2,847	$ 575	$ 495			$ 1,477	$ 1,537			$ 2,078	$ 2,591																																													$ 2,078	$ 2,591	$ 0	$ 0			$ 0	$ 0			$ 2,609	$ 2,288																																														$ 557	$ 256	$ 575	$ 495		$ 1,477	$ 1,537			$ 0	$ 0																																													$ 0	$ 0	$ 0			$ 0	$ 0
Available-for-sale securities			5,160	4,659							142	108	22	20	3	3	92	107	104	105	7	8	24	26	9	13	41	40	309	313	22	21	314	298	39	37	290	231	645	639	44	41	66	62	165	162	466	451					1,845	1,341			511	633	538	451							72	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	466	451					0	0			0	0	4,578	4,187							70	108	22	20	1,341	3	3	88	106	104	105	0	4	0	11	0	12	41	40	309	313	22	21	314	298	39	37	290	231	645	639	44	41	66	62	165	162	0	0					1,845			511	633	44	21							0	0	0	0	0	0	4	1	0	0	7	4	24	15	9	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0				0	0			0	0
Derivative assets			49	70	1,928	2,221			715	439																																																	0	0	0	0			0	0																																																	2,546	2,568	1,843	2,142			703	426																																																	97	92	85	79			12	13																																																(2,594)	(2,590)
Embedded derivative assets			0	0																																																							0	0																																																							0	0																																																							0	0
Total assets			9,896	9,608																																																							2,616	3,042																																																							9,733	9,043																																																							141	113																																																						(2,594)	(2,590)
Derivative liabilities			(19)	(43)	(51)	(73)	0	0	(1,018)	(1,008)																																																	0	0	0	0	0	0	0																																																		(1,058)	(1,071)	(40)	(63)	0	0	(1,018)	(1,008)																																																	(11)	(10)	(11)	(10)	0	0	0																																																	1,050	1,038
Embedded derivative liabilities			(23)	(24)																																																							0	0																																																							0	0																																																							(23)	(24)
Total liabilities			(42)	(67)																																																							0	0																																																							(1,058)	(1,071)																																																							(34)	(34)																																																						1,050	1,038
Total net assets			9,854	9,541																																																							2,616	3,042																																																							8,675	7,972																																																							107	79																																																						(1,544)	(1,552)
Transfers from Level 2 to Level 1	$ 0	$ 53