Equity - Reclassifications out of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($)	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment fair value changes, net	$ (3,138,000)	$ (889,000)	$ (23,297,000)	$ (2,498,000)
Realized gains, net	(2,827,000)	(4,714,000)	(13,513,000)	(14,077,000)
Net Income before Provision for Income Taxes	(33,599,000)	(35,275,000)	(88,946,000)	(87,016,000)
Other than temporary impairments	0	300,000	0	300,000
Other than temporary impairments recognized in income				100,000
Other than temporary impairments recognized in Accumulated other comprehensive income		200,000		200,000
Reclassification out of Accumulated Other Comprehensive Income \| Net Unrealized Gains on Available-for-Sale Securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment fair value changes, net	0	56,000	0	56,000
Realized gains, net	(2,822,000)	(4,804,000)	(12,315,000)	(14,191,000)
Net Income before Provision for Income Taxes	(2,822,000)	$ (4,748,000)	(12,315,000)	(14,135,000)
Other than temporary impairments recognized in income				$ (100,000)
Other than temporary impairments recognized in Accumulated other comprehensive income	$ 0		$ 0

The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 8A
-URI http://asc.fasb.org/extlink&oid=118954083&loc=SL6284422-111562

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- Definition

Amount of income (loss) from continuing operations before deduction of income tax expense (benefit) and income (loss) attributable to noncontrolling interest, and addition of income (loss) from equity method investments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(h)(1)(i))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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- Definition

Amount before tax of other than temporary impairment (OTTI) loss on investments in available-for-sale and held-to-maturity debt securities, recognized in other comprehensive loss.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 35
-Paragraph 35
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-SubTopic 10
-Section 45
-Paragraph 10A
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-URI http://asc.fasb.org/extlink&oid=118930883&loc=SL7669646-108580

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The amount of other than temporary impairment (OTTI) losses on equity securities, OTTI related to credit losses on debt securities, and OTTI losses on debt securities when the entity intends to sell the securities or it is more likely than not that the entity will be required to sell the securities before recovery of its amortized cost basis. Additionally, this item includes OTTI losses recognized during the period on investments accounted for under the cost method of accounting.

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The net realized gains or losses on investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-SubTopic 220
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of investments, not including unrealized gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, held at each balance sheet date and included in earnings for the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
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-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

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