Summary Accounting Policies (Details)	3 Months Ended	6 Months Ended
Jun. 30, 2019 USD ($) item	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) item	Jun. 30, 2018 USD ($)
Investment in Joint Ventures and Variable Interest Entities
Number of Unconsolidated Joint Venture VIEs \| item	0		0
Recourse debt of joint ventures	$ 0		$ 0
Impairment charge relating to investments in unconsolidated joint ventures	$ 0	$ 0	$ 0	$ 0

The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 8A
-URI http://asc.fasb.org/extlink&oid=109979856&loc=SL6284422-111562

Name:	us-gaap_ImpairmentOfInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration