Business Combinations (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended			1 Months Ended	9 Months Ended			0 Months Ended		0 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010	Dec. 30, 2010 US Oncology Holdings, Inc. [Member]	Dec. 31, 2011 US Oncology Holdings, Inc. [Member] Y	Dec. 31, 2011 US Oncology Holdings, Inc. [Member] Service Agreements [Member] Y	Dec. 31, 2011 US Oncology Holdings, Inc. [Member] Customer Lists [Member] Y	Mar. 25, 2012 The Katz Group [Member] Y D	Mar. 31, 2012 The Katz Group [Member]	Mar. 25, 2012 The Katz Group [Member] Service Agreements [Member] Y	Mar. 25, 2012 The Katz Group [Member] Trademarks And Trade Names [Member] Y	Mar. 25, 2012 The Katz Group [Member] Medicine Shop [Member] item	Mar. 25, 2012 The Katz Group [Member] Drug Trading Company [Member] item	Dec. 31, 2011 Level 3 [Member] US Oncology Holdings, Inc. [Member]	Dec. 31, 2011 Level 3 [Member] US Oncology Holdings, Inc. [Member] Service Agreements [Member]	Dec. 31, 2011 Level 3 [Member] US Oncology Holdings, Inc. [Member] Customer Lists [Member]	Mar. 25, 2012 Level 3 [Member] The Katz Group [Member]	Mar. 25, 2012 Level 3 [Member] The Katz Group [Member] Service Agreements [Member]	Mar. 25, 2012 Level 3 [Member] The Katz Group [Member] Trademarks And Trade Names [Member]
Business Acquisition [Line Items]
Number of independent pharmacies												160	850
Working capital adjustments								60
Purchase price of acquisition				$ 2,100				$ 919
Cash consideration				200
Assumption of debt	0	1,891	0	1,900
Useful life-in years					16	18	10	20		20	20
Purchase price allocation of identifiable intangibles														993	721	185	441	317	114
Purchase price allocation assigned to goodwill								506
Goodwill, expected tax deductable amount									$ 287