Investment Securities (Narrative) (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020 USD ($) security	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2020 USD ($) security	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Debt Securities, Available-for-sale [Line Items]
Equity securities without readily determinable fair values	$ 31,200								$ 31,200
Upward adjustments of equity securities without readily determinable fair values									401	$ 505	$ 325
Downward adjustments of equity securities without readily determinable fair values									0	106	0
Impairment of equity securities without readily determinable fair values									2,995	262	1,117
Income tax (benefit) expense	33,507	$ 29,969	$ 9,044	$ 24,271	$ 30,718	$ 35,480	$ 28,707	$ 29,499	96,791	124,404	116,967
Investment securities pledged as collateral	$ 2,400,000				$ 1,700,000				$ 2,400,000	1,700,000
Number of securities by a single non-government sponsored issuer exceeding 10% of shareholders' equity | security	0								0
Investment securities
Debt Securities, Available-for-sale [Line Items]
Income tax (benefit) expense									$ (513)	$ 939	$ (772)