Leases - Finance leases (Details)	6 Months Ended
Jun. 30, 2019 item
Lease as Lessee
Number of finance leases	1
Options to extend - finance leases	true
Minimum
Lease as Lessee
Remaining terms - finance leases	1 year
Maximum
Lease as Lessee
Remaining terms - finance leases	19 years

Indicates (true false) whether lessee has option to extend finance lease.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918673-209980

Name:	us-gaap_LesseeFinanceLeaseExistenceOfOptionToExtend
Namespace Prefix:	us-gaap_
Data Type:	xbrli:booleanItemType
Balance Type:	na
Period Type:	duration