Income Taxes - Components of Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Current income tax expense (benefit)	$ 129,647	$ 134,948	$ 134,626
Deferred income tax expense (benefit)	35,264	35,449	27,535
Income tax expense (benefit)	164,911	170,397	162,161
Shareholders’ equity:
Other comprehensive income (loss)	314,845	405,472	(293,678)
Income tax expense (benefit)	$ 479,756	$ 575,869	$ (131,517)