Investments in Equity Securities (Investments in Equity Securities Available for Sale) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Equity securities	$ 480,620	$ 279,006
Fair Value
Debt Securities, Available-for-sale [Line Items]
Cost	345,099	228,777
Gross unrealized gains	165,210	76,699
Gross unrealized losses	(29,689)	(26,470)
Equity securities	480,620	279,006
Fair Value \| Common stocks
Debt Securities, Available-for-sale [Line Items]
Cost	175,928	113,576
Gross unrealized gains	16,967	4,335
Gross unrealized losses	(26,090)	(19,719)
Equity securities	166,805	98,192
Fair Value \| Preferred stocks
Debt Securities, Available-for-sale [Line Items]
Cost	169,171	115,201
Gross unrealized gains	148,243	72,364
Gross unrealized losses	(3,599)	(6,751)
Equity securities	313,815	180,814
Carrying Value
Debt Securities, Available-for-sale [Line Items]
Equity securities	480,620	279,006
Carrying Value \| Common stocks
Debt Securities, Available-for-sale [Line Items]
Equity securities	166,805	98,192
Carrying Value \| Preferred stocks
Debt Securities, Available-for-sale [Line Items]
Equity securities	$ 313,815	$ 180,814

Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=99377092&loc=SL75136599-209740

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Amount of unrealized gain on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=116654751&loc=SL75117546-209714

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Amount of unrealized loss on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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