Contingencies, Significant Estimates and Concentrations (Details) - USD ($)	3 Months Ended
	Dec. 31, 2016	Sep. 30, 2016
Personal injury actions and other
Loss contingencies
Maximum self-insurance available per claim	$ 5,000,000
Reserve for loss contingencies	35,200,000	$ 38,300,000
Performance and specialty bonds
Loss contingencies
Commitments and contingencies	504,900,000	503,600,000
Standby letters of credit
Loss contingencies
Commitments and contingencies	$ 99,800,000	$ 110,800,000