Other Liabilities - Changes in contract liabilities (Details) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018
Changes in contract liabilities
Contract liabilities - Club initiation fees (Balance at beginning of period)	$ 5,676	$ 5,199
Increases Due To Cash Received	1,663	695
Decreases Due to Revenue Recognized	(882)	(576)
Contract liabilities - Club initiation fees (Balance at end of period)	$ 6,457	$ 5,318

Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130549-203045

Name:	us-gaap_ContractWithCustomerLiabilityRevenueRecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration