Investment Securities (Schedule of Investment Securities) (Details) - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Available-for-sale securities
Amortized Cost	$ 2,316,369,000	$ 2,960,081,000
Gross unrealized gains	40,094,000	98,578,000
Gross unrealized losses	(28,670,000)	(2,820,000)
Fair Value	2,327,793,000	3,055,839,000
Held-to-maturity securities
Amortized Cost	2,942,363,000	579,197,000
Gross unrealized gains	10,609,000	14,784,000
Gross unrealized losses	(52,278,000)	(214,000)
Fair Value	2,900,694,000	593,767,000
Less: Allowance for credit losses	(78,000)	(59,000)
Held-to-maturity securities, net of allowance for credit losses	2,942,285,000	579,138,000
Equity securities with readily determinable fair value
Amortized Cost	86,989,000	87,618,000
Gross unrealized gains	5,354,000	3,674,000
Gross unrealized losses	(1,832,000)	(430,000)
Fair Value	90,511,000	90,862,000
U.S. Treasury
Available-for-sale securities
Amortized Cost	0	304,956,000
Gross unrealized gains	0	15,000
Gross unrealized losses	0	0
Fair Value	0	304,971,000
U.S. Government agencies
Available-for-sale securities
Amortized Cost	50,158,000	80,074,000
Gross unrealized gains	2,349,000	4,439,000
Gross unrealized losses	0	0
Fair Value	52,507,000	84,513,000
Held-to-maturity securities
Amortized Cost	180,192,000	177,959,000
Gross unrealized gains	201,000	2,552,000
Gross unrealized losses	(3,314,000)	0
Fair Value	177,079,000	180,511,000
Municipal
Available-for-sale securities
Amortized Cost	161,618,000	141,244,000
Gross unrealized gains	4,193,000	5,707,000
Gross unrealized losses	(217,000)	(41,000)
Fair Value	165,594,000	146,910,000
Held-to-maturity securities
Amortized Cost	187,486,000	200,707,000
Gross unrealized gains	9,544,000	12,232,000
Gross unrealized losses	(223,000)	(214,000)
Fair Value	196,807,000	212,725,000
Corporate notes
Held-to-maturity securities
Amortized Cost	43,955,000	0
Gross unrealized gains	0	0
Gross unrealized losses	(1,119,000)	0
Fair Value	42,836,000	0
Financial issuers
Available-for-sale securities
Amortized Cost	96,878,000	91,786,000
Gross unrealized gains	418,000	1,363,000
Gross unrealized losses	(2,599,000)	(2,764,000)
Fair Value	94,697,000	90,385,000
Other
Available-for-sale securities
Amortized Cost	1,000,000	1,000,000
Gross unrealized gains	7,000	20,000
Gross unrealized losses	0	0
Fair Value	1,007,000	1,020,000
Mortgage-backed securities
Available-for-sale securities
Amortized Cost	1,901,005,000	2,330,332,000
Gross unrealized gains	32,830,000	86,721,000
Gross unrealized losses	(25,854,000)	(15,000)
Fair Value	1,907,981,000	2,417,038,000
Held-to-maturity securities
Amortized Cost	2,530,730,000	200,531,000
Gross unrealized gains	864,000	0
Gross unrealized losses	(47,622,000)	0
Fair Value	2,483,972,000	200,531,000
Collateralized mortgage obligations
Available-for-sale securities
Amortized Cost	105,710,000	10,689,000
Gross unrealized gains	297,000	313,000
Gross unrealized losses	0	0
Fair Value	106,007,000	$ 11,002,000
Mortgage-backed securities, subprime
Available-for-sale securities
Fair Value	$ 0