Goodwill and other intangibles - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Acquired Finite-Lived Intangible Assets [Line Items]
Increase in goodwill	$ 182,587
Other intangibles, gross carrying amount	72,900	$ 35,000
Accumulated amortization of other intangibles	35,500	30,400
Amortization expense of other intangibles	5,100	$ 4,200
Future amortization expense
Expected amortization expense in 2021	8,100
Expected amortization expense in 2022	6,500
Expected amortization expense in 2023	5,700
Expected amortization expense in 2024	4,400
Expected amortization expense in 2025	$ 3,900
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization period	10 years
Internally-developed technology
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization period	5 years
Title
Acquired Finite-Lived Intangible Assets [Line Items]
Increase in goodwill	$ 118,272
Other intangibles acquired	700
Ancillary Services and Corporate
Acquired Finite-Lived Intangible Assets [Line Items]
Increase in goodwill	64,315
Other intangibles acquired	$ 37,100