Investment Securities - Narrative (Details)	3 Months Ended			12 Months Ended
	Mar. 31, 2022 USD ($) investment_security	Dec. 31, 2021 USD ($) investment_security	Mar. 31, 2021 USD ($)	Dec. 31, 2021 USD ($) investment_security	Jan. 01, 2022 USD ($)
Investment Securities
Net carrying amount of securities transferred from available-for-sale to held-to-maturity	$ 618,678,000		$ 0
Unrealized loss on securities transferred from available-for-sale to held-to-maturity	110,428,000	$ 1,649,000		$ 1,649,000
Investment securities pledged	56,500,000	130,700,000		130,700,000
Accumulated other comprehensive income (loss), net of tax	(144,233,000)	(7,862,000)		(7,862,000)
Investments held-to-maturity, allowance for credit losses	41,000	22,000		22,000
Investments held-to-maturity, provision for credit losses	19,000		0	11,000
Allowance for credit losses on debt securities, Available-for-sale	0	0		$ 0
Available-for-sale securities, provision for credit losses	$ 0	$ 0	0
Available-for-sale and held-to-maturity securities in nonaccrual status | investment_security	0	0		0
Available-for-sale and held-to-maturity securities purchased with deterioration in credit quality | investment_security	0	0		0
Available-for-sale and held-to-maturity collateral dependent | investment_security	0	0		0
FHLB stock	$ 17,300,000	$ 17,300,000		$ 17,300,000
FRB stock	74,600,000	74,500,000		74,500,000
Other stock	25,100,000	25,700,000		25,700,000
Amount of stock repurchased by FHLB	0	0	$ 0
Impairment loss on investments in FHLB, FRB and other stock	0
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent
Investment Securities
Accumulated other comprehensive income (loss) before tax amount	(172,800,000)	(4,700,000)		(4,700,000)
Accumulated other comprehensive income (loss), net of tax	(123,500,000)	(3,300,000)		(3,300,000)
Municipal bonds
Investment Securities
Securities transferred from available-for-sale to held-to-maturity	386,800,000
Net carrying amount of securities transferred from available-for-sale to held-to-maturity	379,900,000
Unrealized loss on securities transferred from available-for-sale to held-to-maturity	101,757,000	1,649,000		1,649,000	$ 6,900,000
Accumulated other comprehensive income (loss), net of tax	(20,800,000)
Mortgage-backed securities
Investment Securities
Securities transferred from available-for-sale to held-to-maturity	255,000,000
Net carrying amount of securities transferred from available-for-sale to held-to-maturity	238,800,000
Unrealized loss on securities transferred from available-for-sale to held-to-maturity	$ 8,671,000	$ 0		$ 0	$ 16,200,000