Earnings per share - Calculation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Numerator:
Net income (loss) attributable to Stewart	$ 26,375	$ (13,467)	$ 38,778	$ (8,809)
Less: Cash paid on Class B Common Shares conversion	0	0	(12,000)	0
Net income (loss) available to common shareholders	$ 26,375	$ (13,467)	$ 26,778	$ (8,809)
Denominator (000):
Basic average shares outstanding	23,371	23,286	23,362	23,631
Diluted average shares outstanding	23,611	23,286	23,596	23,631
Basic earnings (loss) per share attributable to Stewart (in usd per share)	$ 1.13	$ (0.58)	$ 1.15	$ (0.37)
Diluted earnings (loss) per share attributable to Stewart (in usd per share)	$ 1.12	$ (0.58)	$ 1.13	$ (0.37)
Stock Option
Denominator (000):
Average number of dilutive shares relating to share-based incentives	1	0	1	0
Restricted Shares
Denominator (000):
Average number of dilutive shares relating to share-based incentives	239	0	233	0