Investments (Narrative) (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($) Affiliate Business partnership Issuer Security	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) Affiliate Business partnership Issuer Security	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) Issuer Security
Reclassifications from AOCI to net income (loss):
Number of investment in any entity or affiliates greater than 10% of stockholders' equity | Affiliate	0		0
Securities on deposit with state insurance departments	$ 42,600		$ 42,600
Business owned life insurance cost	33,000		33,000
Investment in unconsolidated subsidiaries	$ 312,848		$ 312,848		$ 358,820
Number of LPs / LLCs with investment ownership percent over 25% (in businesses) | Business	4		4
Net impairment losses recognized in earnings	$ 0	$ 30	$ 1,508	$ 78
Portion of impairment losses recognized in other comprehensive income (loss) before taxes	0	36	237	124
Net realized investment (losses) gains	8,838	1,134	150	47,064
Change in unrealized holding gains (losses), equity investments	2,766	(2,157)	(21,012)	27,775
Unrealized gain (loss) on hybrid instrument, net	$ 1,170	$ (408)	$ (190)	$ 2,597
Tax Credit Partnerships Almost 100% Ownership
Reclassifications from AOCI to net income (loss):
Number of tax credit partnerships almost 100% ownership percentage | partnership	2		2
Investment in unconsolidated subsidiaries	$ 11,400		$ 11,400		17,200
Tax Credit Partnerships Almost 100% Ownership | Maximum
Reclassifications from AOCI to net income (loss):
Investment ownership percentage	100.00%		100.00%
Tax Credit Partnerships Less Than 20% Ownership
Reclassifications from AOCI to net income (loss):
Investment in unconsolidated subsidiaries	$ 20,900		$ 20,900		29,200
Tax Credit Partnerships Less Than 20% Ownership | Maximum
Reclassifications from AOCI to net income (loss):
Investment ownership percentage	20.00%		20.00%
Other Limited Partnerships and Limited Liability Company, Greater Than 25% Ownership
Reclassifications from AOCI to net income (loss):
Investment in unconsolidated subsidiaries	$ 48,200		$ 48,200		41,000
Other Limited Partnerships and Limited Liability Company Less than 25% Ownership
Reclassifications from AOCI to net income (loss):
Investment in unconsolidated subsidiaries	232,400		232,400		$ 269,300
Fixed maturities
Reclassifications from AOCI to net income (loss):
Required FAL deposit	98,300		98,300
Cash and cash equivalents
Reclassifications from AOCI to net income (loss):
Required FAL deposit	$ 7,500		$ 7,500
Non government-backed
Reclassifications from AOCI to net income (loss):
Debt securities in unrealized loss position (in securities) | Security	490		490		263
Debt securities in unrealized loss position as percentage of total debt securities held	19.20%		19.20%		12.10%
Issuers in unrealized loss position (in issuers) | Issuer	358		358		204
Single greatest unrealized loss position	$ 700		$ 700		$ 200
Second greatest unrealized loss position	500		500		$ 100
Tax Year 2020 | Tax Credit Partnership Investment Tax Credit Carryforward
Reclassifications from AOCI to net income (loss):
Deferred tax credit for partnership investments	4,500		$ 13,400
Syndicate 1729
Reclassifications from AOCI to net income (loss):
Return of deposit assets	$ 32,300
Proportion of capital provided to support Lloyd's Syndicate 1729	29.00%		29.00%		61.00%