Share Repurchase Programs (Details) - Accelerated Share Repurchase Program [Member] - USD ($)	3 Months Ended			6 Months Ended
	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Mar. 31, 2016
Equity, Class of Treasury Stock [Line Items]
Authorized amount			$ 300,000,000
Stock repurchase program expiration date			15 months
Remaining authorized repurchase amount	$ 152,000,000			$ 152,000,000
Common Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Repurchased amount	$ 110,900,000	$ 37,100,000		$ 148,000,000
Shares repurchased	3,900,000.0	1,200,000.0		5,100,000.0