Fair Value Measurements (Financial Assets and Liabilities Measured at Fair Value On a Recurring Basis) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Mar. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	$ 5,071	$ 5,389
Debt instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	2,863
Debt instruments [Member] | U.S. government and agency obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	2,246	652
Debt instruments [Member] | Municipal debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	12	11
Debt instruments [Member] | Certificates Of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	30	1,599
Debt instruments [Member] | Commercial paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	271	507
Debt instruments [Member] | Corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	167	169
Debt instruments [Member] | U.S. government agency mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	57	60
Debt instruments [Member] | Non-agency residential mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	4	5
Debt instruments [Member] | Non-agency commercial mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	46	43
Debt instruments [Member] | Asset-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	30	27
Equity instruments [Member] | Fixed income short-term floating NAV fund II [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	190
Equity instruments [Member] | Fixed income short-term sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	37	44
Equity instruments [Member] | Fixed income U.S. government sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	274	327
Equity instruments [Member] | Fixed income municipal sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	19	22
Equity instruments [Member] | Investment Grade Corporate Sector Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	265	316
Equity instruments [Member] | Fixed income high-yield sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	37	45
Equity instruments [Member] | Fixed income real return sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	229	274
Equity instruments [Member] | Fixed income mortgage sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	441	520
Equity instruments [Member] | Fixed income asset-backed securities sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	42	50
Equity instruments [Member] | Fixed income emerging market sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	55	66
Equity instruments [Member] | Fixed income international sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	146	171
Equity instruments [Member] | Equity mutual fund - S&P 500 index [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	473	481
Level 3 [Member] | U.S. government and agency obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Reclassification from One Level 3 category to another	2
Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	4,805	3,569
Investments in marketable securities	5,071	5,389
Derivative assets	49	49
Embedded derivative assets		0
Total assets	9,925	10,084
Total liabilities	(22)	(6)
Total net assets	9,903	10,078
Recurring [Member] | Foreign currency swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	420	874
Derivative liabilities	(517)	(252)
Recurring [Member] | Interest rate swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	336	361
Derivative liabilities	(366)	(553)
Recurring [Member] | Debt instruments [Member] | U.S. government and agency obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	2,246	652
Recurring [Member] | Debt instruments [Member] | Municipal debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	12	11
Recurring [Member] | Debt instruments [Member] | Certificates Of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	30	1,599
Recurring [Member] | Debt instruments [Member] | Commercial paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	271	507
Recurring [Member] | Debt instruments [Member] | Corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	167	169
Recurring [Member] | Debt instruments [Member] | U.S. government agency mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	57	60
Recurring [Member] | Debt instruments [Member] | Non-agency residential mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	4	5
Recurring [Member] | Debt instruments [Member] | Non-agency commercial mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	46	43
Recurring [Member] | Debt instruments [Member] | Asset-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	30	27
Recurring [Member] | Equity instruments [Member] | Fixed income short-term floating NAV fund II [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	190
Recurring [Member] | Equity instruments [Member] | Fixed income short-term sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	37	44
Recurring [Member] | Equity instruments [Member] | Fixed income U.S. government sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	274	327
Recurring [Member] | Equity instruments [Member] | Fixed income municipal sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	19	22
Recurring [Member] | Equity instruments [Member] | Investment Grade Corporate Sector Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	265	316
Recurring [Member] | Equity instruments [Member] | Fixed income high-yield sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	37	45
Recurring [Member] | Equity instruments [Member] | Fixed income real return sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	229	274
Recurring [Member] | Equity instruments [Member] | Fixed income mortgage sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	441	520
Recurring [Member] | Equity instruments [Member] | Fixed income asset-backed securities sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	42	50
Recurring [Member] | Equity instruments [Member] | Fixed income emerging market sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	55	66
Recurring [Member] | Equity instruments [Member] | Fixed income international sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	146	171
Recurring [Member] | Equity instruments [Member] | Equity mutual fund - S&P 500 index [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	473	481
Recurring [Member] | Money market instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	1,974	1,424
Restricted Cash Equivalents - money market instruments		1,077
Recurring [Member] | Certificates of deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	2,350	1,437
Recurring [Member] | Commercial paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	300	708
Recurring [Member] | U.S. government and agency obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	181
Recurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	955	730
Investments in marketable securities	1,550	879
Derivative assets	0	0
Embedded derivative assets		0
Total assets	2,505	2,686
Total liabilities	0	0
Total net assets	2,505	2,686
Recurring [Member] | Level 1 [Member] | Foreign currency swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0	0
Derivative liabilities	0	0
Recurring [Member] | Level 1 [Member] | Interest rate swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	0	0
Derivative liabilities	0	0
Recurring [Member] | Level 1 [Member] | Debt instruments [Member] | U.S. government and agency obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	1,077	398
Recurring [Member] | Level 1 [Member] | Debt instruments [Member] | Municipal debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 1 [Member] | Debt instruments [Member] | Certificates Of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 1 [Member] | Debt instruments [Member] | Commercial paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 1 [Member] | Debt instruments [Member] | Corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 1 [Member] | Debt instruments [Member] | U.S. government agency mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 1 [Member] | Debt instruments [Member] | Non-agency residential mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 1 [Member] | Debt instruments [Member] | Non-agency commercial mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 1 [Member] | Debt instruments [Member] | Asset-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 1 [Member] | Equity instruments [Member] | Fixed income short-term floating NAV fund II [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0
Recurring [Member] | Level 1 [Member] | Equity instruments [Member] | Fixed income short-term sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 1 [Member] | Equity instruments [Member] | Fixed income U.S. government sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 1 [Member] | Equity instruments [Member] | Fixed income municipal sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 1 [Member] | Equity instruments [Member] | Investment Grade Corporate Sector Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 1 [Member] | Equity instruments [Member] | Fixed income high-yield sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 1 [Member] | Equity instruments [Member] | Fixed income real return sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 1 [Member] | Equity instruments [Member] | Fixed income mortgage sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 1 [Member] | Equity instruments [Member] | Fixed income asset-backed securities sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 1 [Member] | Equity instruments [Member] | Fixed income emerging market sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 1 [Member] | Equity instruments [Member] | Fixed income international sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 1 [Member] | Equity instruments [Member] | Equity mutual fund - S&P 500 index [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	473	481
Recurring [Member] | Level 1 [Member] | Money market instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	955	730
Restricted Cash Equivalents - money market instruments		1,077
Recurring [Member] | Level 1 [Member] | Certificates of deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Recurring [Member] | Level 1 [Member] | Commercial paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Recurring [Member] | Level 1 [Member] | U.S. government and agency obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0
Recurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	3,850	2,839
Investments in marketable securities	3,427	4,421
Derivative assets	701	1,162
Embedded derivative assets		0
Total assets	7,978	8,422
Total liabilities	(883)	(805)
Total net assets	7,095	7,617
Recurring [Member] | Level 2 [Member] | Foreign currency swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	367	804
Derivative liabilities	(517)	(252)
Recurring [Member] | Level 2 [Member] | Interest rate swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	334	358
Derivative liabilities	(366)	(553)
Recurring [Member] | Level 2 [Member] | Debt instruments [Member] | U.S. government and agency obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	1,167	252
Recurring [Member] | Level 2 [Member] | Debt instruments [Member] | Municipal debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	12	11
Recurring [Member] | Level 2 [Member] | Debt instruments [Member] | Certificates Of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	30	1,599
Recurring [Member] | Level 2 [Member] | Debt instruments [Member] | Commercial paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	271	507
Recurring [Member] | Level 2 [Member] | Debt instruments [Member] | Corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	155	157
Recurring [Member] | Level 2 [Member] | Debt instruments [Member] | U.S. government agency mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	57	60
Recurring [Member] | Level 2 [Member] | Debt instruments [Member] | Non-agency residential mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 2 [Member] | Debt instruments [Member] | Non-agency commercial mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 2 [Member] | Debt instruments [Member] | Asset-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 2 [Member] | Equity instruments [Member] | Fixed income short-term floating NAV fund II [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	190
Recurring [Member] | Level 2 [Member] | Equity instruments [Member] | Fixed income short-term sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	37	44
Recurring [Member] | Level 2 [Member] | Equity instruments [Member] | Fixed income U.S. government sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	274	327
Recurring [Member] | Level 2 [Member] | Equity instruments [Member] | Fixed income municipal sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	19	22
Recurring [Member] | Level 2 [Member] | Equity instruments [Member] | Investment Grade Corporate Sector Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	265	316
Recurring [Member] | Level 2 [Member] | Equity instruments [Member] | Fixed income high-yield sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	37	45
Recurring [Member] | Level 2 [Member] | Equity instruments [Member] | Fixed income real return sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	229	274
Recurring [Member] | Level 2 [Member] | Equity instruments [Member] | Fixed income mortgage sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	441	520
Recurring [Member] | Level 2 [Member] | Equity instruments [Member] | Fixed income asset-backed securities sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	42	50
Recurring [Member] | Level 2 [Member] | Equity instruments [Member] | Fixed income emerging market sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	55	66
Recurring [Member] | Level 2 [Member] | Equity instruments [Member] | Fixed income international sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	146	171
Recurring [Member] | Level 2 [Member] | Equity instruments [Member] | Equity mutual fund - S&P 500 index [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 2 [Member] | Money market instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	1,019	694
Restricted Cash Equivalents - money market instruments		0
Recurring [Member] | Level 2 [Member] | Certificates of deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	2,350	1,437
Recurring [Member] | Level 2 [Member] | Commercial paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	300	708
Recurring [Member] | Level 2 [Member] | U.S. government and agency obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	181
Recurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Investments in marketable securities	94	89
Derivative assets	55	73
Embedded derivative assets		0
Total assets	149	162
Total liabilities	0	0
Total net assets	149	162
Recurring [Member] | Level 3 [Member] | Foreign currency swaps [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	53	70
Derivative liabilities	0	0
Recurring [Member] | Level 3 [Member] | Interest rate swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	2	3
Derivative liabilities	0	0
Recurring [Member] | Level 3 [Member] | Debt instruments [Member] | U.S. government and agency obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	2	2
Recurring [Member] | Level 3 [Member] | Debt instruments [Member] | Municipal debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 3 [Member] | Debt instruments [Member] | Certificates Of Deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 3 [Member] | Debt instruments [Member] | Commercial paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 3 [Member] | Debt instruments [Member] | Corporate debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	12	12
Recurring [Member] | Level 3 [Member] | Debt instruments [Member] | U.S. government agency mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 3 [Member] | Debt instruments [Member] | Non-agency residential mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	4	5
Recurring [Member] | Level 3 [Member] | Debt instruments [Member] | Non-agency commercial mortgage-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	46	43
Recurring [Member] | Level 3 [Member] | Debt instruments [Member] | Asset-backed securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	30	27
Recurring [Member] | Level 3 [Member] | Equity instruments [Member] | Fixed income short-term floating NAV fund II [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0
Recurring [Member] | Level 3 [Member] | Equity instruments [Member] | Fixed income short-term sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 3 [Member] | Equity instruments [Member] | Fixed income U.S. government sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 3 [Member] | Equity instruments [Member] | Fixed income municipal sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 3 [Member] | Equity instruments [Member] | Investment Grade Corporate Sector Fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 3 [Member] | Equity instruments [Member] | Fixed income high-yield sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 3 [Member] | Equity instruments [Member] | Fixed income real return sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 3 [Member] | Equity instruments [Member] | Fixed income mortgage sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 3 [Member] | Equity instruments [Member] | Fixed income asset-backed securities sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 3 [Member] | Equity instruments [Member] | Fixed income emerging market sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 3 [Member] | Equity instruments [Member] | Fixed income international sector fund [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 3 [Member] | Equity instruments [Member] | Equity mutual fund - S&P 500 index [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in marketable securities	0	0
Recurring [Member] | Level 3 [Member] | Money market instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Restricted Cash Equivalents - money market instruments		0
Recurring [Member] | Level 3 [Member] | Certificates of deposit [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Recurring [Member] | Level 3 [Member] | Commercial paper [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Recurring [Member] | Level 3 [Member] | U.S. government and agency obligations [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0
Recurring [Member] | Counterparty Netting & Collateral [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	(707)	(1,186)
Total assets	(707)	(1,186)
Derivative liabilities	861	799
Total liabilities	861	799
Total net assets	$ 154	$ (387)