Guarantees (Details 5)	Dec. 31, 2016 USD ($)
Guarantor Obligations [Line Items]
Guarantor obligations, maximum exposure, undiscounted	$ 98,700,000
Fixed maximum amounts guaranteed by year 2017	33,600,000
Fixed maximum amounts guaranteed by year 2018	4,500,000
Fixed maximum amounts guaranteed by year 2019	56,600,000
Fixed maximum amounts guaranteed by year no maturity date	4,000,000
Amount outstanding under guarantees	0
Letters of credit	30,800,000
Outstanding letters of credit	0
Amount of surety bonds outstanding	516,100,000
Financial Guarantee [Member]
Guarantor Obligations [Line Items]
Guarantor obligations, maximum exposure, undiscounted	$ 63,800,000