Schedule I - Parent Company Financial Information - Statements of Cash Flows (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
Reconciliation of net income (loss) to cash provided (used) by operating activities:
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
Add (deduct):
Depreciation and amortization									30,044	30,298	24,226
Decrease (increase) in receivables – net									7,759	12,894	8,791
Decrease (increase) in other assets – net									391	3,073	(1,878)
(Decrease) increase in payables and accrued liabilities – net									(3,888)	2,088	(6,854)
(Income) losses from subsidiaries									(2,834)	(3,579)	(3,442)
Other – net									7,215	5,668	448
Cash provided by operating activities									122,962	80,514	63,989
Investing activities:
Cash used by investing activities									(56,774)	(68,791)	(78,557)
Financing activities:
Proceeds from notes payable									57,758	52,651	120,273
Payments on notes payable									(60,339)	(22,494)	(60,838)
Cash paid on Class B Common Shares conversion									(12,000)	0	0
Repurchases of Common Stock									(1,053)	(27,950)	(22,048)
Purchase of remaining interest of consolidated subsidiary									(991)	(209)	(20)
Other – net									86	168	(21)
Cash (used) provided by financing activities									(59,342)	(25,550)	26,026
Increase (decrease) in cash and cash equivalents									6,705	(21,491)	6,269
Cash and cash equivalents at beginning of year				179,067				200,558	179,067	200,558	194,289
Cash and cash equivalents at end of year	185,772				179,067				185,772	179,067	200,558
Supplemental information:
Income taxes paid									15,265	14,982	(106)
Interest paid									3,020	1,873	2,616
Stewart Information Services Corporation - Parent Company
Reconciliation of net income (loss) to cash provided (used) by operating activities:
Net income (loss) attributable to Stewart									55,478	(6,204)	29,753
Add (deduct):
Depreciation and amortization									69	162	421
Other losses									0	0	869
Decrease (increase) in receivables – net									245	(596)	(357)
Decrease (increase) in other assets – net									359	(558)	(828)
(Decrease) increase in payables and accrued liabilities – net									(496)	(515)	12,395
(Income) losses from subsidiaries									(47,421)	12,465	(12,837)
Other – net									(6,731)	(4,593)	(31,824)
Cash provided by operating activities									1,503	161	(2,408)
Investing activities:
Dividends from subsidiary									20,000	15,000	25,000
Purchase of property and equipment –net									(22)	0	0
Collections on notes receivables									27,500	0	0
Increases in notes receivables									0	(21,500)	(46,875)
Cash used by investing activities									47,478	(6,500)	(21,875)
Financing activities:
Proceeds from notes payable									20,000	45,000	60,000
Payments on notes payable									(25,125)	(7,000)	0
Dividends paid									(27,840)	(18,010)	(2,334)
Cash paid on Class B Common Shares conversion									(12,000)	0	0
Repurchases of Common Stock									(1,053)	(27,950)	(22,048)
Purchase of remaining interest of consolidated subsidiary									(991)	(209)	(321)
Other – net									86	130	0
Cash (used) provided by financing activities									(46,923)	(8,039)	35,297
Increase (decrease) in cash and cash equivalents									2,058	(14,378)	11,014
Cash and cash equivalents at beginning of year				$ 832				$ 15,210	832	15,210	4,196
Cash and cash equivalents at end of year	$ 2,890				$ 832				2,890	832	15,210
Supplemental information:
Income taxes paid									1	1	24
Interest paid									$ 2,716	$ 1,681	$ 546