Fair Value Measurements - Carrying Value and Fair Value Measurements (Details) - Level 3 - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Carrying Value
Liabilities
Debt, net	$ 1,297,189	$ 1,275,448
Notes receivable	63,954	66,500
Fair Value
Liabilities
Debt, net	1,310,580	1,301,844
Notes receivable	$ 66,454	$ 69,000

Fair value portion of an agreement for an unconditional promise by the maker to pay the holder a definite sum of money at a future date.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.3(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_NotesReceivableFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant