Earnings per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Net income attributable to Stewart	$ 22,377	$ 18,568	$ 18,598	$ 22,657
Denominator (000):
Basic average shares outstanding	23,546	23,444	23,527	23,438
Average number of dilutive shares relating to grants of restricted shares and units	79	176	80	175
Diluted average shares outstanding	23,625	23,620	23,607	23,613
Basic earnings per share attributable to Stewart (in usd per share)	$ 0.95	$ 0.79	$ 0.79	$ 0.97
Diluted earnings per share attributable to Stewart (in usd per share)	$ 0.95	$ 0.79	$ 0.79	$ 0.96