Investments (Narrative) (Details) $ in Millions	12 Months Ended
Dec. 31, 2022 USD ($) item security	Dec. 31, 2021 USD ($) security	Dec. 31, 2020 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Number of investment in unaffiliated issuers \| item	2
Gross gains on investments	$ 4.6		$ 6.7
Realized gains on sale of investments	3.7	$ 5.9
Gross losses on investments	1.5	0.7
Realized losses on sale of investments	1.4	0.5
Proceeds from sale of investment securities	37.2	23.1
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Number of Positions [Abstract]
Other-than-temporary impairment	$ 0.0	0.0
Number of securities sold \| security	1
Debt Securities, Available-for-sale, Realized Gain (Loss), Excluding Other-than-temporary Impairment	$ 0.0
Securities available-for-sale pledged, carrying value	$ 40.9	$ 30.0
Investment in AT&T Inc [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment held in unaffiliated issuers (as percentage)	11.00%
Investment in common stock (as percentage)	29.90%
Investment in debt securities (as percentage)	70.10%
Investment in Pilot Travel Centers LLC [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment held in unaffiliated issuers (as percentage)	15.80%
Number of investment grade debt securities \| item	3
Equity Securities [Member]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Number of Positions [Abstract]
Number of debt securities with unrealized loss \| security	17	14
Number of debt securities with unrealized loss, less than 12 months \| security	8	10
Number of debt securities with unrealized loss, greater than 12 months \| security	9	4
Debt Securities [Member]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Number of Positions [Abstract]
Number of debt securities with unrealized loss \| security	228	100
Number of debt securities with unrealized loss, less than 12 months \| security	181	74
Number of debt securities with unrealized loss, greater than 12 months \| security	47	26

Amount of realized gain on investment in debt and equity securities.

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