Equity - Reclassifications out of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment fair value changes, net	$ (11,444,000)	$ (10,332,000)	$ (34,741,000)	$ (12,830,000)
Realized gains, net	(4,714,000)	(7,275,000)	(18,227,000)	(21,352,000)
Provision for income taxes	(114,000)	4,919,000	3,102,000	12,343,000
Net Income before Provision for Income Taxes	(34,196,000)	(45,840,000)	(123,142,000)	(132,856,000)
Other than temporary impairments	0	400,000	0	600,000
Other than temporary impairments recognized in income		300,000		500,000
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	33,000	0	89,000
Realized gains, net	(3,492,000)	(7,247,000)	(15,807,000)	(21,438,000)
Provision for income taxes	0	1,528,000	0	1,528,000
Net Income before Provision for Income Taxes	$ (3,492,000)	(5,686,000)	$ (15,807,000)	(19,821,000)
Other-than-temporary impairment loss portion recognized in earnings		$ (100,000)		$ (100,000)