Fair value of financial instruments - Schedule of Financial Liabilities Not Measured at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Carrying Value
Financial liabilities not recorded at fair value
Total liabilities	$ 1,250,466	$ 1,040,658
Carrying Value | Term Loan
Financial liabilities not recorded at fair value
Total liabilities		980,658
Carrying Value | Revolving Credit Facility
Financial liabilities not recorded at fair value
Total liabilities	84,667	60,000
Carrying Value | Property Loan
Financial liabilities not recorded at fair value
Total liabilities	101,183
Fair Value | Level 1
Financial liabilities not recorded at fair value
Total liabilities	0	0
Fair Value | Level 1 | Term Loan
Financial liabilities not recorded at fair value
Total liabilities		0
Fair Value | Level 1 | Revolving Credit Facility
Financial liabilities not recorded at fair value
Total liabilities	0	0
Fair Value | Level 1 | Property Loan
Financial liabilities not recorded at fair value
Total liabilities	0
Fair Value | Level 2
Financial liabilities not recorded at fair value
Total liabilities	0	0
Fair Value | Level 2 | Term Loan
Financial liabilities not recorded at fair value
Total liabilities		0
Fair Value | Level 2 | Revolving Credit Facility
Financial liabilities not recorded at fair value
Total liabilities	0	0
Fair Value | Level 2 | Property Loan
Financial liabilities not recorded at fair value
Total liabilities	0
Fair Value | Level 3
Financial liabilities not recorded at fair value
Total liabilities	1,183,081	1,043,214
Fair Value | Level 3 | Term Loan
Financial liabilities not recorded at fair value
Total liabilities		983,214
Fair Value | Level 3 | Revolving Credit Facility
Financial liabilities not recorded at fair value
Total liabilities	84,780	$ 60,000
Fair Value | Level 3 | Property Loan
Financial liabilities not recorded at fair value
Total liabilities	110,848
Term Loan | Carrying Value | Term Loan
Financial liabilities not recorded at fair value
Total liabilities	974,103
Term Loan | Fair Value | Level 1 | Term Loan
Financial liabilities not recorded at fair value
Total liabilities	0
Term Loan | Fair Value | Level 2 | Term Loan
Financial liabilities not recorded at fair value
Total liabilities	0
Term Loan | Fair Value | Level 3 | Term Loan
Financial liabilities not recorded at fair value
Total liabilities	893,061
Term A1 Loan | Carrying Value | Term Loan
Financial liabilities not recorded at fair value
Total liabilities	33,701
Term A1 Loan | Fair Value | Level 1 | Term Loan
Financial liabilities not recorded at fair value
Total liabilities	0
Term A1 Loan | Fair Value | Level 2 | Term Loan
Financial liabilities not recorded at fair value
Total liabilities	0
Term A1 Loan | Fair Value | Level 3 | Term Loan
Financial liabilities not recorded at fair value
Total liabilities	35,179
Term A2 Loan | Carrying Value | Term Loan
Financial liabilities not recorded at fair value
Total liabilities	29,850
Term A2 Loan | Fair Value | Level 1 | Term Loan
Financial liabilities not recorded at fair value
Total liabilities	0
Term A2 Loan | Fair Value | Level 2 | Term Loan
Financial liabilities not recorded at fair value
Total liabilities	0
Term A2 Loan | Fair Value | Level 3 | Term Loan
Financial liabilities not recorded at fair value
Total liabilities	31,158
Term A3 Loan | Carrying Value | Term Loan
Financial liabilities not recorded at fair value
Total liabilities	26,962
Term A3 Loan | Fair Value | Level 1 | Term Loan
Financial liabilities not recorded at fair value
Total liabilities	0
Term A3 Loan | Fair Value | Level 2 | Term Loan
Financial liabilities not recorded at fair value
Total liabilities	0
Term A3 Loan | Fair Value | Level 3 | Term Loan
Financial liabilities not recorded at fair value
Total liabilities	$ 28,055