Equity investees - Summarized Aggregate Financial Information for Equity Investees (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Revenues	$ 2,288,432	$ 1,940,008	$ 1,907,672
Net income	154,905	78,615	47,523
Total assets	1,978,575	1,592,785
Notes payable	966,169	839,026
Total stockholders’ equity attributable to Stewart	1,005,112	747,306
Equity method investment, nonconsolidated investee or group of investees
Schedule of Equity Method Investments [Line Items]
Revenues	26,396	19,660	22,286
Net income	7,101	6,231	4,729
Total assets	36,222	36,865	33,268
Notes payable	27,133	27,841	24,833
Total stockholders’ equity attributable to Stewart	$ 4,868	$ 6,341	$ 6,292