Schedule I - Parent Company Financial Information - Statements of Operations and Retained Earnings (Detail) - USD ($) $ 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
Revenues
Investment income									$ 18,925	$ 16,850	$ 16,806
Total 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
Expenses
Employee costs									604,353	658,266	624,326
Other operating expenses, including $276 each year to affiliates									363,986	381,954	347,276
Depreciation and amortization									30,044	30,298	24,226
Interest									3,062	2,096	3,236
Total expenses									1,918,614	2,024,192	1,819,018
Income before taxes and income (losses) from subsidiaries									88,026	9,693	51,812
Income tax expense									19,605	5,650	13,503
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
Retained earnings at beginning of year				455,519					455,519
Cash dividends on Common Stock									(27,840)	(18,010)	(2,334)
Cash paid on Class B Common Shares conversion									(12,000)	0	0
Cumulative effect adjustment on adoption of new accounting pronouncement	631				0				631	0	0
Retained earnings at end of year	471,788				455,519				471,788	455,519
Stewart Information Services Corporation - Parent Company
Revenues
Investment income									20,000	15,000	25,087
Other losses									0	0	(869)
Other income									1,252	922	90
Total revenues									21,252	15,922	24,308
Expenses
Employee costs									832	156	1,110
Other operating expenses, including $276 each year to affiliates									6,641	7,617	3,806
Depreciation and amortization									69	162	421
Interest									2,726	1,726	2,054
Total expenses									10,268	9,661	7,391
Income before taxes and income (losses) from subsidiaries									10,984	6,261	16,917
Income tax expense									2,928	0	1
Income (losses) from subsidiaries									47,422	(12,465)	12,837
Net income (loss) attributable to Stewart									55,478	(6,204)	29,753
Retained earnings at beginning of year				$ 455,519				$ 479,733	455,519	479,733	452,314
Cash dividends on Common Stock									(27,840)	(18,010)	(2,334)
Retained earnings at end of year	$ 471,788				$ 455,519				$ 471,788	$ 455,519	$ 479,733