Earnings per share - Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Numerator (in usd):
Net (loss) income attributable to Stewart									$ (6,204)	$ 29,753	$ 63,026
Interest expense, net of tax effects									0	1,006	1,408
If-converted net (loss) income attributable to Stewart									$ (6,204)	$ 30,759	$ 64,434
Denominator (000) (shares):
Basic average shares outstanding									23,544	22,778	22,096
Average number of dilutive shares relating to convertible senior notes									0	1,641	2,467
Diluted average shares outstanding									23,544	24,710	24,741
Basic (loss) earnings per share attributable to Stewart (usd per share)									$ (0.26)	$ 1.31	$ 2.85
Diluted (loss) earnings per share attributable to Stewart (usd per share)	$ 0.11	$ (0.58)	$ 0.72	$ (0.52)	$ 0.49	$ 0.97	$ 0.27	$ (0.54)	$ (0.26)	$ 1.24	$ 2.60
Employee Stock Option
Denominator (000) (shares):
Dilutive average number of shares relating to share-based payment arrangements									0	2	0
Restricted Stock
Denominator (000) (shares):
Dilutive average number of shares relating to share-based payment arrangements									0	289	178