Schedule I - Financial Information of the Registrant (Parent Company) - Statements of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of net income (loss) to cash provided by operating activities:
Net income (loss) attributable to Stewart	$ 15,060	$ 10,944	$ 18,568	$ 4,087	$ 16,699	$ 26,375	$ 23,599	$ (11,195)	$ 48,659	$ 55,478	$ (6,204)
Add (deduct):
Depreciation and amortization									25,878	30,044	30,298
(Increase) decrease in receivables – net									(6,910)	7,759	12,894
(Increase) decrease in other assets – net									(4,512)	391	3,073
Increase (decrease) in payables and accrued liabilities – net									1,933	(3,888)	2,088
(Income) losses from subsidiaries									(2,163)	(2,834)	(3,579)
Other – net									483	0	(872)
Cash provided by operating activities									108,068	122,962	80,514
Investing activities:
Cash used by investing activities									(103,897)	(56,774)	(68,791)
Financing activities:
Proceeds from notes payable									56,493	57,758	52,651
Payments on notes payable									(56,467)	(60,339)	(22,494)
Cash paid on Class B Common Shares conversion									0	(12,000)	0
Repurchases of Common Stock									(727)	(1,053)	(27,950)
Purchase of remaining interest of consolidated subsidiary									(1,810)	(991)	(209)
Other – net									0	86	168
Cash used by financing activities									(43,595)	(59,342)	(25,550)
(Decrease) increase in cash and cash equivalents									(35,693)	6,705	(21,491)
Cash and cash equivalents at beginning of year				185,772				179,067	185,772	179,067	200,558
Cash and cash equivalents at end of year	150,079				185,772				150,079	185,772	179,067
Supplemental information:
Income taxes paid									(1,642)	15,265	14,982
Interest paid									3,466	3,020	1,873
Parent Company
Reconciliation of net income (loss) to cash provided by operating activities:
Net income (loss) attributable to Stewart									48,659	55,478	(6,204)
Add (deduct):
Depreciation and amortization									5	69	162
(Increase) decrease in receivables – net									(81)	245	(596)
(Increase) decrease in other assets – net									(1,576)	359	(558)
Increase (decrease) in payables and accrued liabilities – net									563	(496)	(515)
(Income) losses from subsidiaries									(36,062)	(47,421)	12,465
Other – net									1,705	(6,731)	(4,593)
Cash provided by operating activities									13,213	1,503	161
Investing activities:
Dividends from subsidiary									20,000	20,000	15,000
Purchase of property and equipment –net									0	(22)	0
Collections on notes receivables									23,375	27,500	0
Increases in notes receivables									(16,000)	0	(21,500)
Contributions to a subsidiary									(7,184)	0	0
Cash used by investing activities									20,191	47,478	(6,500)
Financing activities:
Proceeds from notes payable									16,000	20,000	45,000
Payments on notes payable									(10,000)	(25,125)	(7,000)
Dividends paid									(28,135)	(27,840)	(18,010)
Cash paid on Class B Common Shares conversion									0	(12,000)	0
Repurchases of Common Stock									(727)	(1,053)	(27,950)
Purchase of remaining interest of consolidated subsidiary									(1,810)	(991)	(209)
Other – net									0	86	130
Cash used by financing activities									(24,672)	(46,923)	(8,039)
(Decrease) increase in cash and cash equivalents									8,732	2,058	(14,378)
Cash and cash equivalents at beginning of year				$ 2,890				$ 832	2,890	832	15,210
Cash and cash equivalents at end of year	$ 11,622				$ 2,890				11,622	2,890	832
Supplemental information:
Income taxes paid									0	1	1
Interest paid									$ 3,128	$ 2,716	$ 1,681