Accumulated Other Comprehensive Income (Loss) (AOCI) (Components of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax, Beginning Balance	$ 39,541
Stockholders equity attributable to noncontrolling interest, Beginning Balance	11,676
Accumulated other comprehensive income (loss) including non-controlling interest, Beginning Balance	39,542
Change in unrealized gains (losses) on debt securities	(131,434)
Change in unrealized gains (losses) on debt securities for which credit-related portion was recognized in earnings	(387)
Change in foreign currency translation adjustment	3,532
Amortization of net actuarial loss	1,690
Amortization of prior service credit	(326)
Tax effect	31,555	$ (4,526)
Accumulated other comprehensive income (loss), net of tax, Ending Balance	(55,828)
Stockholders equity attributable to noncontrolling interest, Ending Balance	10,402
Accumulated other comprehensive income (loss) including non-controlling interest, Ending Balance	(55,828)
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	171,752
Change in unrealized gains (losses) on debt securities	(131,433)
Change in unrealized gains (losses) on debt securities for which credit-related portion was recognized in earnings	(387)
Tax effect	32,075
Accumulated other comprehensive income (loss), debt securities, available-for-sale, adjustment, after tax, Ending Balance	72,007
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	(37,990)
Change in foreign currency translation adjustment	3,532
Tax effect	(158)
Accumulated other comprehensive income (loss), foreign currency translation adjustment, net of tax, Ending Balance	(34,616)
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	(94,221)
Amortization of net actuarial loss	1,690
Amortization of prior service credit	(326)
Tax effect	(362)
Accumulated other comprehensive (income) Loss, defined benefit plan, after Tax, Ending Balance	(93,219)
Accumulated Other Comprehensive Income (Loss) Attributable to First American Financial Corporation
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), net of tax, Beginning Balance	39,541
Change in unrealized gains (losses) on debt securities	(131,433)
Change in unrealized gains (losses) on debt securities for which credit-related portion was recognized in earnings	(387)
Change in foreign currency translation adjustment	3,532
Amortization of net actuarial loss	1,690
Amortization of prior service credit	(326)
Tax effect	31,555
Accumulated other comprehensive income (loss), net of tax, Ending Balance	(55,828)
Accumulated Other Comprehensive Income (Loss) Attributable to NCI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Stockholders equity attributable to noncontrolling interest, Beginning Balance	1
Change in unrealized gains (losses) on debt securities	$ (1)