Guarantees (Details 4)	Dec. 31, 2019 USD ($)
Guarantor Obligations [Line Items]
Guarantor obligations, maximum exposure, undiscounted	$ 174,800,000
Fixed maximum amounts guaranteed by year 2020	162,600,000
Fixed maximum amounts guaranteed by year 2021	700,000
Fixed maximum amounts guaranteed by year 2022	400,000
Fixed maximum amounts guaranteed by year 2023	500,000
Fixed maximum amounts guaranteed by year 2024	500,000
Fixed maximum amounts guaranteed, thereafter	1,100,000
No scheduled maturity date	9,000,000.0
Amount outstanding under guarantees that is reflected on balance sheet	0
Letters of credit	33,200,000
Letters of credit set to expire - 2020	32,700,000
Letters of credit set to expire - 2021	500,000
Outstanding letters of credit	0
Amount of surety bonds outstanding	$ 1,100,000,000