Significant acquisitions - Narratives (Details)		3 Months Ended		6 Months Ended
	May 26, 2017 USD ($) property	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Business Acquisition [Line Items]
Total purchase price				$ 68,632,000	$ 0
Business acquisition costs		$ 13,211,000	$ 0	13,753,000	0
Proceeds from credit facility	$ 45,000,000		$ 0	45,000,000	$ 0
Goodwill		$ 123,023,000		$ 123,023,000		$ 113,343,000
Cap Juluca
Business Acquisition [Line Items]
Number of rooms | property	96
Transaction value	$ 84,512,000
Total purchase price	68,652,000
Business acquisition costs	13,753,000
Working capital adjustment	2,107,000
Other intangible assets	6,100,000
Goodwill	$ 5,500,000
Lease term	125 years