Related-Party Transactions - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Mar. 08, 2018	Feb. 06, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Par value of common shares (in USD per share)	$ 0.01		$ 0.01		$ 0.01		$ 0.01
YF ART Holdings L.P.
Related Party Transaction [Line Items]
Shares pledged in financing arrangement (in shares)					54,952,774
Shares pledged in financing arrangement as a percentage of shares issue and outstanding					38.60%
2018 Senior Secured Credit Facilities | Credit Facility
Related Party Transaction [Line Items]
Commitments from lending group under credit facility						$ 925,000,000
Principal Owner | Goldman
Related Party Transaction [Line Items]
Interest expense	$ 700,000	$ 600,000	$ 2,300,000	$ 1,800,000
Principal Owner | Goldman | 2018 Senior Secured Credit Facilities | Credit Facility
Related Party Transaction [Line Items]
Commitments from lending group under credit facility	$ 45,000,000		$ 45,000,000
Commitments from lending group under credit facility, percentage	4.90%		4.90%
Principal Owner | Affiliate of Goldman | Australia Term Loan | Term Loans
Related Party Transaction [Line Items]
Lender participation in loans	2.50%		2.50%
Principal Owner | Affiliate of Goldman | New Zealand Term Loan | Term Loans
Related Party Transaction [Line Items]
Lender participation in loans	31.80%		31.80%
Principal Owner | YF ART Holdings L.P.
Related Party Transaction [Line Items]
Number of shares committed to be owned by related party (in shares)					27,500,000.0
Primary and Secondary Offering | Principal Owner | Goldman
Related Party Transaction [Line Items]
Underwriting fee paid			$ 5,000,000