Equity - Reclassifications out of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment fair value changes, net	$ (35,500,000)	$ 25,689,000	$ (10,374,000)
Realized gains, net	(23,821,000)	(27,041,000)	(13,355,000)
Provision for income taxes	7,440,000	11,088,000	11,752,000
Net income before provision for income taxes	(176,623,000)	(130,688,000)	$ (152,158,000)
Other than temporary impairments	0	1,000,000
Other-than-temporary Impairment Loss, Debt Securities, Portion Recognized in Earnings		100,000
Accumulated other comprehensive income, other-than-temporary impairments		1,000,000
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	89,000
Realized gains, net	(19,967,000)	(27,178,000)
Provision for income taxes	0	1,528,000
Net income before provision for income taxes	$ (19,967,000)	$ (25,561,000)