Property, plant and equipment - Narrative (Details) - USD ($)		3 Months Ended		6 Months Ended
	Jul. 12, 2017	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Property, Plant and Equipment [Abstract]
Depreciation expense		$ 15,600,000	$ 13,600,000	$ 31,000,000	$ 25,800,000
Interest expense capitalized on qualifying assets		$ 1,400,000	$ 0	2,100,000	0
Property, Plant and Equipment [Line Items]
Consideration paid upon closing				40,058,000	12,673,000
Remaining balance due upon opening of resort				$ 290,000	$ 277,000
Land
Property, Plant and Equipment [Line Items]
Total consideration	$ 56,200,000
Consideration paid upon closing	45,600,000
Remaining balance due upon opening of resort	$ 10,600,000
Period post beginning of construction of resorts that payment may be due	2 years