Commitments and Contingencies (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($) transaction	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 12, 2017 USD ($)
Commitments and Contingencies [Line Items]
Limited payment guaranties	$ 13,000
Number of transactions with recourse | transaction	2
Notes receivable outstanding	$ 115,676		$ 93,392
Other commitment	10,100
Other commitment, payment	2,400
Construction loan		$ 34,900
Forgivable Notes Receivable
Commitments and Contingencies [Line Items]
Other commitment	220,700
Capital contributions to joint ventures
Commitments and Contingencies [Line Items]
Other commitment	12,200
Notes Receivable
Commitments and Contingencies [Line Items]
Notes receivable outstanding	$ 24,400			$ 49,100