Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
General financing percent of purchase price, offer for qualified purchasers	90.00%
Typical financing term for qualified purchasers	10 years
Management contracts, initial term	3 years
Management contracts, renewal term	1 year
Notes receivable past due	$ 17.0	$ 12.9
Accounting Standards Update 2016-02 [Member]
Schedule of Equity Method Investments [Line Items]
Lease assets and liabilities recognized, term	12 months
Quantification of the effect of adopting the new accounting standard or change in accounting principle expected	$ 40.2