Earnings per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Numerator:
Net income attributable to Stewart	$ 17,554	$ 10,944	$ 36,151	$ 33,601
Denominator (000):
Basic average shares outstanding	23,556	23,448	23,537	23,442
Average number of dilutive shares relating to grants of restricted shares and units	143	116	140	129
Diluted average shares outstanding	23,699	23,564	23,677	23,571
Basic earnings per share attributable to Stewart (in usd per share)	$ 0.75	$ 0.47	$ 1.54	$ 1.43
Diluted earnings per share attributable to Stewart (in usd per share)	$ 0.74	$ 0.46	$ 1.53	$ 1.43