Guarantees (Details 3)	Sep. 30, 2017 USD ($)
Guarantor Obligations [Line Items]
Guarantor obligations, maximum exposure, undiscounted	$ 119,400,000
Fixed maximum amounts guaranteed by year 2017	2,500,000
Fixed maximum amounts guaranteed by year 2018	21,300,000
Fixed maximum amounts guaranteed by year 2019	15,800,000
Fixed maximum amounts guaranteed by year 2020	72,600,000
Fixed maximum amounts guaranteed by year 2021.	500,000
Fixed maximum amounts guaranteed, thereafter	2,700,000
No scheduled maturity date	4,000,000.0
Amount outstanding under guarantees that is reflected on balance sheet	0
Letters of credit	34,000,000.0
Letters of credit set to expire - 2017	29,200,000
Letters of credit set to expire - 2018	4,800,000
Outstanding letters of credit	0
Amount of surety bonds outstanding	556,800,000
Financial guarantee [Member]
Guarantor Obligations [Line Items]
Guarantor obligations, maximum exposure, undiscounted	$ 57,400,000