Investments (Investment Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investments [Line Items]
Total investment income	$ 140,586	$ 146,868	$ 141,483
Less: Investment expense	(5,728)	(5,605)	(5,645)
Net investment income	134,858	141,263	135,838
Fixed Maturity Securities [Member]
Investments [Line Items]
Total investment income	100,166	102,254	102,198
Equity Securities [Member]
Investments [Line Items]
Total investment income	37,598	32,233	30,496
Short-term Investments [Member]
Investments [Line Items]
Total investment income	$ 2,822	$ 12,381	$ 8,789