Investment Securities - Income Earned on Securities (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Non-taxable:
Total	$ 27,128	$ 13,473	$ 48,701	$ 32,416
Held-to-maturity
Taxable:
Taxable	837	288	1,350	459
Non-taxable:
Non-taxable	3,030	68	5,034	140
Available-for-sale
Taxable:
Taxable	13,757	7,086	23,364	19,667
Non-taxable:
Non-taxable	$ 9,504	$ 6,031	$ 18,953	$ 12,150