Debt (Aggregate Borrowing Information) (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Line of Credit Facility [Line Items]
Unused credit lines	$ 760,600,000	$ 764,500,000
Financial Services [Member]
Line of Credit Facility [Line Items]
Available credit lines	520,000,000	475,000,000
Unused credit lines	$ 171,588,000	$ 37,196,000
Weighted-average interest rate	4.27%	3.55%