Earnings per share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands			1 Months Ended	3 Months Ended								12 Months Ended
	Apr. 27, 2016	Jan. 26, 2016	Apr. 30, 2016	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Numerator:
Net income (loss) attributable to Stewart				$ 16,699	$ 26,375	$ 23,599	$ (11,195)	$ 2,605	$ (13,467)	$ 17,106	$ (12,448)	$ 55,478	$ (6,204)	$ 29,753
Cash paid on Class B Common Shares conversion												(12,000)	0	0
Net income (loss) for calculating basic EPS												43,478	(6,204)	29,753
Add: Interest expense, net of tax effects												0	0	1,006
Adjusted net income (loss) for calculating diluted EPS												$ 43,478	$ (6,204)	$ 30,759
Denominator (000):
Basic average shares outstanding (shares)												23,364	23,544	22,778
Average number of dilutive shares relating to convertible senior notes (shares)												0	0	1,641
Diluted average shares outstanding (shares)												23,472	23,544	24,710
Basic earnings (loss) per share attributable to Stewart (USD per share)												$ 1.86	$ (0.26)	$ 1.31
Diluted earnings (loss) per share attributable to Stewart (USD per share)				$ 0.71	$ 1.12	$ 0.49	$ (0.48)	$ 0.11	$ (0.58)	$ 0.72	$ (0.52)	$ 1.85	$ (0.26)	$ 1.24
Conversion, Class B Common Stock To Common Stock
Numerator:
Cash paid on Class B Common Shares conversion	$ (12,000)	$ (12,000)	$ (12,000)									$ (12,000)
Employee Stock Option
Denominator (000):
Average number of dilutive shares (shares)												0	0	2
Restricted Stock
Denominator (000):
Average number of dilutive shares (shares)												108	0	289