Earnings per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Numerator:
Net income attributable to Stewart	$ 94,819	$ 34,146	$ 149,055	$ 39,322
Denominator
Basic average shares outstanding (in shares)	26,798	23,656	26,767	23,647
Average number of dilutive shares relating to options (in shares)	189	0	154	0
Average number of dilutive shares relating to grants of restricted units and shares (in shares)	136	100	117	110
Diluted average shares outstanding (in shares)	27,123	23,756	27,038	23,757
Basic earnings per share attributable to Stewart (in usd per share)	$ 3.54	$ 1.44	$ 5.57	$ 1.66
Diluted earnings per share attributable to Stewart (in usd per share)	$ 3.50	$ 1.44	$ 5.51	$ 1.66