Quarterly financial information (unaudited) (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	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
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 525,764	$ 553,210	$ 489,437	$ 438,229	$ 497,403	$ 555,705	$ 531,906	$ 448,871	$ 2,006,640	$ 2,033,885	$ 1,870,830
Net (loss) income 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
Diluted (loss) earnings 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