Earnings per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator:
Net income attributable to Stewart	$ 34,146	$ 19,306	$ 39,322	$ 12,540
Denominator
Basic average shares outstanding (in shares)	23,656	23,614	23,647	23,605
Average number of dilutive shares relating to grants of restricted shares and units (in shares)	100	144	110	145
Diluted average shares outstanding (in shares)	23,756	23,758	23,757	23,750
Basic earnings per share attributable to Stewart (in usd per share)	$ 1.44	$ 0.82	$ 1.66	$ 0.53
Diluted earnings per share attributable to Stewart (in usd per share)	$ 1.44	$ 0.81	$ 1.66	$ 0.53