Schedule I - Parent Company Financial Information - Balance Sheets (Parenthetical) (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Balance Sheet Statements, Captions [Line Items]
Accounts payable and accrued liabilities	$ 115,640,000	$ 118,082,000
Treasury stock, common shares (shares)	352,161	352,161
Common Stock
Condensed Balance Sheet Statements, Captions [Line Items]
Common stock, par value (USD per share)	$ 1	$ 1	$ 1
Common stock, shares authorized (shares)	50,000,000	50,000,000
Common stock, shares issued (shares)	23,783,440	22,643,255
Common stock, shares outstanding (shares)	23,431,279	22,291,094
Class B Common Stock
Condensed Balance Sheet Statements, Captions [Line Items]
Common stock, par value (USD per share)	$ 1	$ 1	$ 1
Common stock, shares authorized (shares)	0	1,500,000
Common stock, shares issued (shares)	0	1,050,012
Common stock, shares outstanding (shares)	0	1,050,012
Stewart Information Services Corporation - Parent Company
Condensed Balance Sheet Statements, Captions [Line Items]
Trade and other	$ 848,000	$ 1,093,000
Accounts payable and accrued liabilities	$ 24,812,000	$ 22,781,000
Treasury stock, common shares (shares)	352,161	352,161
Stewart Information Services Corporation - Parent Company | Common Stock
Condensed Balance Sheet Statements, Captions [Line Items]
Common stock, par value (USD per share)	$ 1	$ 1
Common stock, shares authorized (shares)	50,000,000	50,000,000
Common stock, shares issued (shares)	23,783,440	22,643,255
Common stock, shares outstanding (shares)	23,431,279	22,291,094
Stewart Information Services Corporation - Parent Company | Class B Common Stock
Condensed Balance Sheet Statements, Captions [Line Items]
Common stock, par value (USD per share)	$ 1	$ 1
Common stock, shares authorized (shares)	0	1,500,000
Common stock, shares issued (shares)	0	1,050,012
Common stock, shares outstanding (shares)	0	1,050,012
Subsidiaries
Condensed Balance Sheet Statements, Captions [Line Items]
Treasury stock, common shares (shares)	145,820	145,820
Undistributed earnings	$ 522,104	$ 514,522