Condensed Consolidating Financial Statements (Details 2) (USD $) In Millions	May 31, 2011	May 31, 2010	May 31, 2009	May 31, 2008
CURRENT ASSETS
Cash and cash equivalents	$ 2,328	$ 1,952	$ 2,292	$ 1,539
Receivables, less allowances	4,581	4,163
Spare parts, supplies, fuel, prepaid expenses and other, less allowances	766	640
Deferred income taxes	610	529
Total current assets	8,285	7,284
PROPERTY AND EQUIPMENT, AT COST	33,686	31,302
Less accumulated depreciation and amortization	18,143	16,917
Net property and equipment	15,543	14,385
GOODWILL	2,326	2,200	2,229
Other assets	1,231	1,033
ASSETS	27,385	24,902
CURRENT LIABILITIES
Current portion of long-term debt	18	262
Accrued salaries and employee benefits	1,268	1,146
Accounts payable	1,702	1,522
Accrued expenses	1,894	1,715
Total current liabilities	4,882	4,645
LONG-TERM DEBT, LESS CURRENT PORTION	1,667	1,668
OTHER LONG-TERM LIABILITIES
Deferred income taxes	1,336	891
Other liabilities	4,280	3,887
Total other long-term liabilities	5,616	4,778
STOCKHOLDERS' INVESTMENT	15,220	13,811	13,626	14,851
LIABILITIES AND STOCKHOLDERS' INVESTMENT	27,385	24,902
Parent Company Member
CURRENT ASSETS
Cash and cash equivalents	1,589	1,310	1,768	1,101
Receivables, less allowances		1
Spare parts, supplies, fuel, prepaid expenses and other, less allowances	77	5
Total current assets	1,666	1,316
PROPERTY AND EQUIPMENT, AT COST	24	23
Less accumulated depreciation and amortization	18	18
Net property and equipment	6	5
INVESTMENT IN SUBSIDIARIES	15,404	13,850
Other assets	1,652	1,527
ASSETS	18,728	16,698
CURRENT LIABILITIES
Current portion of long-term debt		250
Accrued salaries and employee benefits	50	36
Accounts payable		8
Accrued expenses	198	47
Total current liabilities	248	341
LONG-TERM DEBT, LESS CURRENT PORTION	1,000	1,000
INTERCOMPANY PAYABLE	1,095	702
OTHER LONG-TERM LIABILITIES
Other liabilities	1,165	844
Total other long-term liabilities	1,165	844
STOCKHOLDERS' INVESTMENT	15,220	13,811
LIABILITIES AND STOCKHOLDERS' INVESTMENT	18,728	16,698
Guarantor Subsidiaries Member
CURRENT ASSETS
Cash and cash equivalents	279	258	272	166
Receivables, less allowances	3,696	3,425
Spare parts, supplies, fuel, prepaid expenses and other, less allowances	645	581
Deferred income taxes	598	492
Total current assets	5,218	4,756
PROPERTY AND EQUIPMENT, AT COST	31,916	29,193
Less accumulated depreciation and amortization	17,071	15,801
Net property and equipment	14,845	13,392
GOODWILL	1,564	1,551
INVESTMENT IN SUBSIDIARIES	2,705	2,619
Other assets	1,039	801
ASSETS	25,371	23,119
CURRENT LIABILITIES
Current portion of long-term debt	18	12
Accrued salaries and employee benefits	1,071	955
Accounts payable	1,385	1,196
Accrued expenses	1,563	1,488
Total current liabilities	4,037	3,651
LONG-TERM DEBT, LESS CURRENT PORTION	667	668
INTERCOMPANY PAYABLE	222	430
OTHER LONG-TERM LIABILITIES
Deferred income taxes	2,842	2,253
Other liabilities	3,001	2,921
Total other long-term liabilities	5,843	5,174
STOCKHOLDERS' INVESTMENT	14,602	13,196
LIABILITIES AND STOCKHOLDERS' INVESTMENT	25,371	23,119
Non Guarantor Subsidiaries Member
CURRENT ASSETS
Cash and cash equivalents	546	443	304	272
Receivables, less allowances	912	782
Spare parts, supplies, fuel, prepaid expenses and other, less allowances	44	54
Deferred income taxes	12	37
Total current assets	1,514	1,316
PROPERTY AND EQUIPMENT, AT COST	1,746	2,086
Less accumulated depreciation and amortization	1,054	1,098
Net property and equipment	692	988
INTERCOMPANY RECEIVABLE	1,317	1,132
GOODWILL	762	649
Other assets	63	99
ASSETS	4,348	4,184
CURRENT LIABILITIES
Accrued salaries and employee benefits	147	155
Accounts payable	430	422
Accrued expenses	133	180
Total current liabilities	710	757
OTHER LONG-TERM LIABILITIES
Deferred income taxes	17	32
Other liabilities	114	122
Total other long-term liabilities	131	154
STOCKHOLDERS' INVESTMENT	3,507	3,273
LIABILITIES AND STOCKHOLDERS' INVESTMENT	4,348	4,184
Consolidation Eliminations Member
CURRENT ASSETS
Cash and cash equivalents	(86)	(59)	(52)
Receivables, less allowances	(27)	(45)
Total current assets	(113)	(104)
INTERCOMPANY RECEIVABLE	(1,317)	(1,132)
INVESTMENT IN SUBSIDIARIES	(18,109)	(16,469)
Other assets	(1,523)	(1,394)
ASSETS	(21,062)	(19,099)
CURRENT LIABILITIES
Accounts payable	(113)	(104)
Total current liabilities	(113)	(104)
INTERCOMPANY PAYABLE	(1,317)	(1,132)
OTHER LONG-TERM LIABILITIES
Deferred income taxes	(1,523)	(1,394)
Total other long-term liabilities	(1,523)	(1,394)
STOCKHOLDERS' INVESTMENT	(18,109)	(16,469)
LIABILITIES AND STOCKHOLDERS' INVESTMENT	$ (21,062)	$ (19,099)