Bank revolving credit notes - Additional Information (Details) - USD ($) $ in Thousands		3 Months Ended	6 Months Ended		12 Months Ended
	Sep. 26, 2019	Dec. 31, 2021	Jun. 30, 2022	Dec. 31, 2020	Dec. 31, 2021
Line Of Credit Facility [Line Items]
Revolving credit notes		$ 67,610	$ 76,063		$ 67,610
A&R Credit Agreement [Member]
Line Of Credit Facility [Line Items]
Minimum interest coverage ratio			3.00%
Maximum consolidated leverage ratio			3.25%
A&R Credit Agreement [Member] | The Agent [Member]
Line Of Credit Facility [Line Items]
Credit agreement additional borrowing capacity through accordion feature	$ 100,000
Credit agreement maturity date	Sep. 26, 2024
Second Amendment [Member]
Line Of Credit Facility [Line Items]
Minimum interest coverage ratio			3.00%
Maximum consolidated leverage ratio			3.25%
Debt instrument covenant description			The Second Amendment provided the Company with temporary changes to the total leverage ratio covenant for the period from June 30, 2020, through December 31, 2021, or such earlier date as the Company may elect (Covenant Relief Period), in return for certain increases in interest rates, fees and restrictions on certain activities of the Company, including capital expenditures, acquisitions, dividends and share repurchases. New pricing, which took effect for the quarters ending on and after September 30, 2020, includes interest at a fluctuating London Interbank Offered Rate (LIBOR) (at a floor of 75 basis points), plus 1.00% to 2.75%, along with the commitment fee ranging from 20 to 50 basis points.
Floor rate			0.75%
Leverage ratio		3.25%		4.25%
Consolidated leverage ratio			1.52%
Interest coverage ratios			18.34%
Second Amendment [Member] | Minimum [Member]
Line Of Credit Facility [Line Items]
Debt instrument commitment fee percentage			0.20%
Second Amendment [Member] | Minimum [Member] | LIBOR [Member]
Line Of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate			1.00%
Second Amendment [Member] | Maximum [Member]
Line Of Credit Facility [Line Items]
Debt instrument commitment fee percentage			0.50%
Second Amendment [Member] | Maximum [Member] | LIBOR [Member]
Line Of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate			2.75%
Third Amendment [Member]
Line Of Credit Facility [Line Items]
Capital expenditure incurred					35,000
Third Amendment [Member] | Maximum [Member]
Line Of Credit Facility [Line Items]
Capital expenditure incurred					$ 70,000
Fourth Amendment [Member]
Line Of Credit Facility [Line Items]
Capital expenditure incurred			$ 35,000
Fourth Amendment [Member] | Maximum [Member]
Line Of Credit Facility [Line Items]
Capital expenditure incurred			$ 65,000
Revolving Credit Facility [Member]
Line Of Credit Facility [Line Items]
Interest rate			2.06%		1.75%
Revolving commitments fee percentage			0.20%		0.20%
Revolving credit notes		$ 67,610	$ 76,063		$ 67,610
Revolving Credit Facility [Member] | A&R Credit Agreement [Member] | The Agent [Member]
Line Of Credit Facility [Line Items]
Credit agreement borrowing capacity	$ 200,000
Letter of Credit Sub-facility [Member] | A&R Credit Agreement [Member] | The Agent [Member]
Line Of Credit Facility [Line Items]
Credit agreement borrowing capacity	5,000
Swingline Facility [Member] | A&R Credit Agreement [Member] | The Agent [Member]
Line Of Credit Facility [Line Items]
Credit agreement borrowing capacity	$ 20,000