Stockholders' Equity and Earnings per Share (Details) (USD $) In Millions, except Share data, unless otherwise specified	1 Months Ended		3 Months Ended		6 Months Ended		12 Months Ended		3 Months Ended		1 Months Ended					3 Months Ended	1 Months Ended
	Nov. 30, 2013	Nov. 30, 2012	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013	Sep. 30, 2013	Mar. 18, 2013	Mar. 31, 2014 First Group of Tranches [Member]	Mar. 31, 2014 Second Group of Tranches [Member]	Mar. 31, 2013 Walgreens Warrant 1 [Member]	Mar. 31, 2013 Walgreens Warrant 2 [Member]	Mar. 31, 2013 Alliance Boots Warrant 1 [Member]	Mar. 31, 2013 Alliance Boots Warrant 2 [Member]	Nov. 30, 2012 November 2012 Share Repurchase Program [Member]	Mar. 31, 2014 November 2012 Share Repurchase Program [Member]	Aug. 31, 2013 August 2013 Share Repurchase Program [Member]
Stockholders' Equity and Earnings per Share [Abstract]
Dividend Increase Percentage	12.00%
Common Stock, Dividends, Per Share, Declared		$ 0.235	$ 0.235	$ 0.21	$ 0.47	$ 0.42
Basic			229,409,000	230,422,000	229,852,000	231,409,000
Incremental Common Shares Attributable To Share Based Payment Arrangements			4,863,000	4,165,000	4,985,000	3,898,000
Incremental Common Shares Attributable to Call Options and Warrants			1,996,000	0	1,813,000	0
Diluted			236,268,000	234,587,000	236,650,000	235,307,000
Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount			2,300,000	0	1,800,000	0
Equity, Class of Treasury Stock [Line Items]
Stock Repurchase Program, Authorized Amount															$ 750.00		$ 750.00
Treasury Stock Value Acquired Cost Method																269.80
Treasury Stock, Shares, Acquired																4,100,000
Stock Repurchase Program Remaining Authorized Amount																93.20
Class of Warrant or Right [Line Items]
Class of Warrant or Right, Date from which Warrants or Rights are Exercisable											Mar. 01, 2016	Mar. 01, 2017	Mar. 01, 2016	Mar. 01, 2017
Class of Warrant or Right, Number of Securities Called by Warrants or Rights											11,348,456	11,348,456	11,348,456	11,348,456
Class of Warrant or Right, Exercise Price of Warrants or Rights											$ 51.50	$ 52.50	$ 51.50	$ 52.50
Shares to Which Framework Agreement Allows Open Market Purchases				19,859,795		19,859,795
Percentage of Common Stock Purchases in Open Market Granted under Framework Agreement				0.07		0.07
Fair Value per Share of First Tranche of Warrants			$ 15.09		$ 15.09
Fair Value per Share of Second Tranche of Warrants			$ 15.75		$ 15.75
Full Value of Warrants			700.00		700.00			242.40
Forward Contract Indexed to Issuer's Equity [Line Items]
Forward Contract Indexed to Issuer's Equity, Forward Rate									$ 51.50	$ 52.50
Derivative, Cost of Hedge			$ 205.30				$ 163.40
Percentage of Warrant Dilution Intended to be Hedged with Contract			60.00%
Shares Covered Under Derviative Purchases			11,900,000		11,900,000		15,300,000