Equity Award Plans - Weighted-Average Assumptions for Option Grants (Details)	4 Months Ended	12 Months Ended
	Jan. 31, 2015	Jan. 30, 2016	Sep. 30, 2014	Sep. 30, 2013
Weighted-average assumptions for option grants
Expected dividend yield	5.60%	5.70%	3.20%	3.50%
Expected price volatility	38.10%	36.10%	49.10%	59.60%
Risk-free interest rate	1.80%	1.40%	1.40%	0.80%
Expected life	5 years 4 months 24 days	5 years	4 years 8 months 12 days	5 years 6 months