Segment Information (Schedule of Selected Financial Information) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Revenues	$ 1,491,157	$ 1,454,429	$ 2,788,545	$ 2,771,472
Income (loss) before income taxes	201,968	184,154	295,033	268,034
Depreciation and amortization	31,058	30,145	60,805	60,292
Capital expenditures	39,931	38,525	63,532	70,091
Direct premiums and escrow fees	661,582	641,080	1,205,460	1,168,089
Agent premiums	559,004	554,028	1,086,718	1,128,610
Information and other	208,752	201,851	397,410	384,360
Net investment income	56,334	39,609	99,126	72,649
Net realized investment gains (losses)	5,485	17,861	(169)	17,764
Operating Segments
Segment Reporting Information [Line Items]
Revenues	1,489,228	1,452,072	2,788,077	2,765,284
Direct premiums and escrow fees	661,582	641,080	1,205,460	1,168,089
Agent premiums	559,004	554,028	1,086,718	1,128,610
Information and other	209,019	202,117	397,942	384,891
Net investment income	54,138	36,986	98,126	65,930
Net realized investment gains (losses)	5,485	17,861	(169)	17,764
Operating Segments | Title Insurance and Services
Segment Reporting Information [Line Items]
Revenues	1,369,040	1,336,910	2,554,505	2,539,857
Income (loss) before income taxes	209,642	197,305	312,023	295,548
Depreciation and amortization	29,343	28,557	57,460	57,108
Capital expenditures	34,884	35,916	55,955	66,309
Direct premiums and escrow fees	548,616	532,236	982,768	954,195
Agent premiums	559,004	554,028	1,086,718	1,128,610
Information and other	206,095	199,243	392,116	379,278
Net investment income	51,737	34,665	93,137	61,280
Net realized investment gains (losses)	3,588	16,738	(234)	16,494
Operating Segments | Specialty Insurance
Segment Reporting Information [Line Items]
Revenues	120,188	115,162	233,572	225,427
Income (loss) before income taxes	10,121	9,560	20,021	19,601
Depreciation and amortization	1,677	1,547	3,269	3,098
Capital expenditures	5,047	2,609	7,577	3,782
Direct premiums and escrow fees	112,966	108,844	222,692	213,894
Information and other	2,924	2,874	5,826	5,613
Net investment income	2,401	2,321	4,989	4,650
Net realized investment gains (losses)	1,897	1,123	65	1,270
Corporate
Segment Reporting Information [Line Items]
Revenues	2,208	2,646	1,027	6,764
Income (loss) before income taxes	(17,795)	(22,711)	(37,011)	(47,115)
Depreciation and amortization	38	41	76	86
Capital expenditures	0	0	0	0
Eliminations
Segment Reporting Information [Line Items]
Revenues	(279)	(289)	(559)	(576)
Income (loss) before income taxes	0	0	0	0
Depreciation and amortization	0	0	0	0
Capital expenditures	$ 0	$ 0	$ 0	$ 0