Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Net income	$ 242,260	$ 122,044	$ 158,873
Debt securities available-for-sale:
Net change in unrealized (losses) gains on debt securities available-for-sale	(67,652)	39,880	52,299
Related income tax benefit (expense)	16,112	(9,727)	(11,958)
Net securities gains reclassified into earnings	(56)	(2,540)	(227)
Related income tax expense	13	604	52
Net effect on other comprehensive income for the period	(51,583)	28,217	40,166
Debt securities held-to-maturity:
Amortization of unrealized gain transferred from debt securities available-for-sale		(32)	(222)
Related income tax expense		7	54
Net effect on other comprehensive income for the period		(25)	(168)
Defined benefit plans:
Amortization of net loss and prior service costs	2,521	3,000	3,042
Related income tax benefit	(609)	(714)	(729)
Recognition of unrealized gain (loss)	17,386	(420)	(4,250)
Related income tax (expense) benefit	(4,194)	100	1,011
Net effect on other comprehensive income for the period	15,104	1,966	(926)
Total other comprehensive (loss) gain	(36,479)	30,158	39,072
Comprehensive income	$ 205,781	$ 152,202	$ 197,945