Subsequent events (Details) - USD ($) $ / shares in Units, $ in Thousands			6 Months Ended
	Jul. 28, 2023	Jul. 06, 2023	Jun. 30, 2023	Jun. 30, 2022	May 31, 2023	Mar. 31, 2023	Dec. 31, 2022	Dec. 13, 2022	Jul. 29, 2022	May 24, 2022	Mar. 31, 2022	Feb. 28, 2022	Dec. 31, 2021	May 15, 2020
Subsequent Events [Line Items]
Payments for repurchase of common stock			$ 7,285	$ 46,375
Class A Stock
Subsequent Events [Line Items]
Common stock, outstanding (in shares)			10,884,575	11,270,944		10,975,723	10,868,556	10,867,660	11,251,930	11,863,559	12,156,174	12,322,073	12,447,036	12,636,523
Class A Stock | Modified Dutch Auction Tender Offer
Subsequent Events [Line Items]
Authorized amount					$ 30,000
Class A Stock | Minimum | Modified Dutch Auction Tender Offer
Subsequent Events [Line Items]
Stock repurchase program, price (in dollars per share)					$ 34.00
Class A Stock | Maximum | Modified Dutch Auction Tender Offer
Subsequent Events [Line Items]
Stock repurchase program, price (in dollars per share)					$ 40.00
Class A Stock | Subsequent Event
Subsequent Events [Line Items]
Quarterly dividend payable amount per share (in dollars per share)	$ 0.15
Common stock, outstanding (in shares)		10,447,392
Class A Stock | Subsequent Event | Modified Dutch Auction Tender Offer
Subsequent Events [Line Items]
Stock repurchase program, price (in dollars per share)		$ 40.00
Stock repurchased and cancellation (in shares)		437,183
Payments for repurchase of common stock		$ 17,490
Class B Stock
Subsequent Events [Line Items]
Common stock, outstanding (in shares)			99,665				99,665
Class B Stock | Subsequent Event
Subsequent Events [Line Items]
Quarterly dividend payable amount per share (in dollars per share)	$ 0.15