Contingencies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended	3 Months Ended	1 Months Ended	3 Months Ended
	Dec. 31, 1992 defendant	Mar. 31, 2015	Nov. 30, 2012 company	Sep. 30, 2014 company
Environmental litigation with respect to Lowry Landfill site
Contingencies
Approximate number of other companies named in a lawsuit with respect to Lowry Landfill	38
Waste Management litigation
Contingencies
Response cost related to site, minimum before the company may be asked to make payments		$ 319
Period before projected completion of project when response cost is expected to exceed minimum amount		3 years
Estimated additional cleanup costs		10
Estimated additional site costs for the potentially responsible party (PRP) group		1
Environmental litigation with respect to Lower Duwamish site
Contingencies
Number of additional potentially responsible parties (PRPs)				20
Site cleanup costs				100
Number of companies whose data is reviewed upon			30
Period over which data is reviewed			3 years
Environmental litigation with respect to Lower Duwamish site | Minimum
Contingencies
Number of potentially responsible parties (PRPs)			50
Number of potentially responsible parties (PRP)whose data is under review			2
Forecast | Environmental litigation with respect to Lower Duwamish site
Contingencies
Expected future remediation costs				$ 342