Segment Information (Schedule of Selected Financial Information) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Revenues	$ 2,025,745	$ 1,412,943
Income (loss) before income taxes	306,022	72,324
Depreciation and amortization	38,298	31,449
Capital expenditures	30,999	31,224
Direct premiums and escrow fees	785,675	620,637
Agent premiums	845,292	599,682
Information and other	278,892	211,512
Net investment income	49,053	45,874
Net realized investment gains (losses)	66,833	(64,762)
Operating Segments
Segment Reporting Information [Line Items]
Revenues	2,021,538	1,422,594
Direct premiums and escrow fees	785,675	620,637
Agent premiums	845,292	599,682
Information and other	279,152	211,712
Net investment income	44,586	62,252
Net realized investment gains (losses)	66,833	(71,689)
Operating Segments | Title Insurance and Services
Segment Reporting Information [Line Items]
Revenues	1,885,058	1,300,625
Income (loss) before income taxes	321,630	72,976
Depreciation and amortization	36,713	29,517
Capital expenditures	30,469	28,423
Direct premiums and escrow fees	657,497	501,301
Agent premiums	845,292	599,682
Information and other	275,404	208,273
Net investment income	42,652	59,668
Net realized investment gains (losses)	64,213	(68,299)
Operating Segments | Specialty Insurance
Segment Reporting Information [Line Items]
Revenues	136,480	121,969
Income (loss) before income taxes	6,261	12,857
Depreciation and amortization	1,549	1,894
Capital expenditures	530	2,801
Direct premiums and escrow fees	128,178	119,336
Agent premiums	0	0
Information and other	3,748	3,439
Net investment income	1,934	2,584
Net realized investment gains (losses)	2,620	(3,390)
Corporate
Segment Reporting Information [Line Items]
Revenues	5,066	(9,311)
Income (loss) before income taxes	(21,869)	(13,509)
Depreciation and amortization	36	38
Capital expenditures	0	0
Eliminations
Segment Reporting Information [Line Items]
Revenues	(859)	(340)
Income (loss) before income taxes	0	0
Depreciation and amortization	0	0
Capital expenditures	$ 0	$ 0