Accumulated Other Comprehensive Income (Loss) (AOCI) - Components of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax, Beginning Balance	$ (92)
Tax effect	249	$ 42	$ (21)
Accumulated other comprehensive income (loss), net of tax, Ending Balance	(868)	(92)
Unrealized Gains (Losses) on Debt Securities Attributable to First American Financial Corporation
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), debt securities, available-for-sale, adjustment, after tax, Beginning Balance	29	172	84
Change in unrealized gains (losses) on debt securities	(1,045)	(189)	116
Change in unrealized gains (losses) on debt securities for which credit-related portion was recognized in earnings			1
Tax effect	264	46	(29)
Accumulated other comprehensive income (loss), debt securities, available-for-sale, adjustment, after tax, Ending Balance	752	29	172
Foreign Currency Translation Adjustment Attributable to First American Financial Corporation
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), foreign currency translation adjustment, net of tax, Beginning Balance	(39)	(38)	(52)
Change in foreign currency translation adjustment	(43)	(2)	14
Tax effect	1	1
Accumulated other comprehensive income (loss), foreign currency translation adjustment, net of tax, Ending Balance	(81)	(39)	(38)
Pension Benefit Adjustment Attributable to First American Financial Corporation
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive (income) Loss, defined benefit plan, after Tax, Beginning Balance	(82)	(94)	(73)
Net actuarial (loss) gain	57	11	(31)
Amortization of net actuarial loss	6	7	5
Amortization of prior service credit		(1)	(3)
Tax effect	(16)	(5)	8
Accumulated other comprehensive (income) Loss, defined benefit plan, after Tax, Ending Balance	(35)	(82)	(94)
Accumulated Other Comprehensive Income/(loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax, Beginning Balance	(92)	(40)	41
Change in unrealized gains (losses) on debt securities	(1,045)	(189)	116
Change in unrealized gains (losses) on debt securities for which credit-related portion was recognized in earnings			1
Change in foreign currency translation adjustment	(43)	(2)	14
Net actuarial (loss) gain	57	11	(31)
Amortization of net actuarial loss	6	7	5
Amortization of prior service credit		(1)	(3)
Tax effect	249	42	(21)
Accumulated other comprehensive income (loss), net of tax, Ending Balance	$ (868)	$ (92)	$ (40)