Earnings per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator:
Net income attributable to Stewart	$ 55,909	$ 66,108	$ 95,232	$ 78,648
Denominator
Basic average shares outstanding (in shares)	25,148	23,616	24,151	23,608
Average number of dilutive shares relating to grants of restricted shares and units (in shares)	149	157	105	172
Diluted average shares outstanding (in shares)	25,297	23,773	24,256	23,780
Basic earnings per share attributable to Stewart (in usd per share)	$ 2.22	$ 2.80	$ 3.94	$ 3.33
Diluted earnings per share attributable to Stewart (in usd per share)	$ 2.21	$ 2.78	$ 3.93	$ 3.31