Common Stock Repurchases (Details) - USD ($) shares in Millions	3 Months Ended		9 Months Ended
	Aug. 31, 2017	Aug. 31, 2016	Aug. 31, 2017	Aug. 31, 2016	Sep. 30, 2017	Mar. 31, 2016
Common Stock Repurchases [Abstract]
Common stock repurchased and retired (in shares)	0.6	0.4	1.5	2.8
Common stock repurchased and retired	$ 19,000,000	$ 11,500,000	$ 43,900,000	$ 71,500,000
Equity, Class of Treasury Stock [Line Items]
Remaining authorized repurchase amount	$ 91,400,000		$ 91,400,000			$ 214,500,000
March 2016 Share Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Authorized amount for share repurchase programs						$ 100,000,000.0
Subsequent Event [Member]
Equity, Class of Treasury Stock [Line Items]
Authorized amount for share repurchase programs					$ 250,000,000