Condensed Consolidating Financial Statements (Details 2) (USD $) In Millions, unless otherwise specified	Nov. 30, 2014	May 31, 2014	Nov. 30, 2013	May 31, 2013
CURRENT ASSETS
Cash and cash equivalents	$ 2,266	$ 2,908	$ 3,935	$ 4,917
Receivables, less allowances	5,592	5,460
Spare parts, supplies, fuel, prepaid expenses and other, less allowances	857	793
Deferred income taxes	497	522
Total current assets	9,212	9,683
PROPERTY AND EQUIPMENT, AT COST	41,616	40,691
Less accumulated depreciation and amortization	21,723	21,141
Net property and equipment	19,893	19,550
GOODWILL	2,734	2,790
Other assets	1,145	1,047
ASSETS	32,984	33,070
CURRENT LIABILITIES
Current portion of long-term debt		1
Accrued salaries and employee benefits	1,219	1,277
Accounts payable	1,968	1,971
Accrued expenses	1,986	2,063
Total current liabilities	5,173	5,312
LONG-TERM DEBT, LESS CURRENT PORTION	4,735	4,736
OTHER LONG-TERM LIABILITIES
Deferred income taxes	2,104	2,114
Other liabilities	5,409	5,631
Total other long-term liabilities	7,513	7,745
STOCKHOLDERS' INVESTMENT	15,563	15,277
LIABILITIES AND STOCKHOLDERS' INVESTMENT	32,984	33,070
Parent Company Member
CURRENT ASSETS
Cash and cash equivalents	1,048	1,756	2,808	3,892
Receivables, less allowances	1	2
Spare parts, supplies, fuel, prepaid expenses and other, less allowances	76	59
Total current assets	1,125	1,817
PROPERTY AND EQUIPMENT, AT COST	28	28
Less accumulated depreciation and amortization	22	22
Net property and equipment	6	6
INVESTMENT IN SUBSIDIARIES	21,850	20,785
Other assets	2,051	2,088
ASSETS	25,032	24,696
CURRENT LIABILITIES
Accrued salaries and employee benefits	33	55
Accounts payable	60	2
Accrued expenses	374	405
Total current liabilities	467	462
LONG-TERM DEBT, LESS CURRENT PORTION	4,487	4,487
INTERCOMPANY PAYABLE	2,698	2,323
OTHER LONG-TERM LIABILITIES
Other liabilities	1,817	2,147
Total other long-term liabilities	1,817	2,147
STOCKHOLDERS' INVESTMENT	15,563	15,277
LIABILITIES AND STOCKHOLDERS' INVESTMENT	25,032	24,696
Guarantor Subsidiaries Member
CURRENT ASSETS
Cash and cash equivalents	482	441	492	405
Receivables, less allowances	4,453	4,338
Spare parts, supplies, fuel, prepaid expenses and other, less allowances	719	674
Deferred income taxes	474	501
Total current assets	6,128	5,954
PROPERTY AND EQUIPMENT, AT COST	39,258	38,303
Less accumulated depreciation and amortization	20,458	19,899
Net property and equipment	18,800	18,404
INTERCOMPANY RECEIVABLE	1,172	1,058
GOODWILL	1,552	1,552
INVESTMENT IN SUBSIDIARIES	3,747	3,754
Other assets	862	747
ASSETS	32,261	31,469
CURRENT LIABILITIES
Current portion of long-term debt		1
Accrued salaries and employee benefits	1,011	1,042
Accounts payable	1,403	1,530
Accrued expenses	1,404	1,444
Total current liabilities	3,818	4,017
LONG-TERM DEBT, LESS CURRENT PORTION	248	249
OTHER LONG-TERM LIABILITIES
Deferred income taxes	4,021	4,059
Other liabilities	3,344	3,230
Total other long-term liabilities	7,365	7,289
STOCKHOLDERS' INVESTMENT	20,830	19,914
LIABILITIES AND STOCKHOLDERS' INVESTMENT	32,261	31,469
Non Guarantor Subsidiaries Member
CURRENT ASSETS
Cash and cash equivalents	869	861	775	717
Receivables, less allowances	1,189	1,151
Spare parts, supplies, fuel, prepaid expenses and other, less allowances	62	60
Deferred income taxes	23	21
Total current assets	2,143	2,093
PROPERTY AND EQUIPMENT, AT COST	2,330	2,360
Less accumulated depreciation and amortization	1,243	1,220
Net property and equipment	1,087	1,140
INTERCOMPANY RECEIVABLE	1,526	1,265
GOODWILL	1,182	1,238
Other assets	237	250
ASSETS	6,175	5,986
CURRENT LIABILITIES
Accrued salaries and employee benefits	175	180
Accounts payable	689	620
Accrued expenses	208	214
Total current liabilities	1,072	1,014
OTHER LONG-TERM LIABILITIES
Deferred income taxes	88	93
Other liabilities	248	254
Total other long-term liabilities	336	347
STOCKHOLDERS' INVESTMENT	4,767	4,625
LIABILITIES AND STOCKHOLDERS' INVESTMENT	6,175	5,986
Consolidation Eliminations Member
CURRENT ASSETS
Cash and cash equivalents	(133)	(150)	(140)	(97)
Receivables, less allowances	(51)	(31)
Total current assets	(184)	(181)
INTERCOMPANY RECEIVABLE	(2,698)	(2,323)
INVESTMENT IN SUBSIDIARIES	(25,597)	(24,539)
Other assets	(2,005)	(2,038)
ASSETS	(30,484)	(29,081)
CURRENT LIABILITIES
Accounts payable	(184)	(181)
Total current liabilities	(184)	(181)
INTERCOMPANY PAYABLE	(2,698)	(2,323)
OTHER LONG-TERM LIABILITIES
Deferred income taxes	(2,005)	(2,038)
Total other long-term liabilities	(2,005)	(2,038)
STOCKHOLDERS' INVESTMENT	(25,597)	(24,539)
LIABILITIES AND STOCKHOLDERS' INVESTMENT	$ (30,484)	$ (29,081)