Basis of Condensed Consolidated Financial Statements (Narrative) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Basis Of Condensed Consolidated Financial Statements [Line Items]
Depreciation and amortization	$ 36,000	$ 24,491	$ 96,292	$ 70,905
Net realized investment gains	(7,001)	9,516	10,763	22,692
Title plants and other indexes	566,599		566,599		$ 564,309
Personnel costs	599,380	$ 438,692	1,458,928	$ 1,239,129
Other assets	216,150		216,150		202,460
Accounts payable and accrued liabilities	741,569		741,569		$ 793,955
Out-of-Period Adjustments
Basis Of Condensed Consolidated Financial Statements [Line Items]
Depreciation and amortization	4,700
Net realized investment gains	(1,800)
Title plants and other indexes	(6,500)		(6,500)
Other assets	(8,500)		(8,500)
Accounts payable and accrued liabilities	500		$ 500
Out-of-Period Adjustments | Title Insurance and Services
Basis Of Condensed Consolidated Financial Statements [Line Items]
Personnel costs	$ 9,000