Related-Party Transactions - Additional Information (Details) - USD ($) $ in Thousands			1 Months Ended	3 Months Ended		9 Months Ended
	Sep. 18, 2018	Jan. 23, 2018	Mar. 31, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Related Party Transaction [Line Items]
Underwriting fees paid						$ 0	$ 8,205
Public Offering - Goldman Sachs
Related Party Transaction [Line Items]
Number of shares sold (in shares)	9,083,280		8,061,228
Ownership percentage	9.90%
Public Offering - Goldman Sachs | Goldman
Related Party Transaction [Line Items]
Refunds from underwriters	$ 700
IPO - Shares From Goldman
Related Party Transaction [Line Items]
Number of shares sold (in shares)		5,163,716
Ownership percentage		16.70%
IPO
Related Party Transaction [Line Items]
Number of shares sold (in shares)		33,350,000
Underwriting fees paid		$ 40,000
IPO | Goldman
Related Party Transaction [Line Items]
Refunds from underwriters		$ 1,600
Common Stock | Goldman
Related Party Transaction [Line Items]
Shares converted (in shares)		28,808,224
Principal Owner | Goldman
Related Party Transaction [Line Items]
Interest expense				$ 400	$ 700	1,200	$ 2,300
Underwriting fees paid	$ 5,000		$ 2,600
Principal Owner | Goldman | 2018 Senior Unsecured Credit Facility | Credit Facility
Related Party Transaction [Line Items]
Commitments from lending group under credit facility				$ 90,000		$ 90,000
Commitments from lending group under credit facility, percentage				7.10%		7.10%
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%
Goldman Fees | Principal Owner | Goldman
Related Party Transaction [Line Items]
Fees paid to related party						$ 15,200