Stock Repurchase Program (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	1 Months Ended			3 Months Ended	12 Months Ended	26 Months Ended	1 Months Ended			0 Months Ended	3 Months Ended	7 Months Ended	26 Months Ended
	Jan. 31, 2013	Aug. 31, 2012	Aug. 31, 2011	Dec. 31, 2013	Sep. 30, 2013	Sep. 30, 2013	Jan. 31, 2013 Maximum	Aug. 31, 2012 Maximum	Aug. 31, 2011 Maximum	Aug. 16, 2011 Accelerated Share Repurchase	Sep. 30, 2011 Accelerated Share Repurchase	Mar. 07, 2012 Accelerated Share Repurchase	Sep. 30, 2013 Rule 10b5-1 Repurchase Plan and Open Market Purchases
Stock Repurchase Program
Stock repurchase additional authorized amount	$ 500.0	$ 300.0	$ 200.0
Authorized amount of stock repurchase							1,000.0	500.0	200.0	100.0
Shares repurchased and retired under the agreement						26.6					4.3	4.8	21.8
Total cost of shares repurchased under the agreement						635.3							535.3
Remaining repurchase amount of shares pursuant to the plan					$ 364.7
Average price per share of stock repurchased under the agreement (in dollars per share)						$ 23.88						$ 20.97	$ 24.52
Shares repurchased in transactions that were settled in first quarter of fiscal 2014				0.1