Acquisition and Discontinued Operations - Income from Discontinued Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss and loss adjustment expenses	$ (2)	$ 19	$ (710)	$ (1,628)
Net investment income	897	629	2,345	2,277
Gain on change in fair value of equity investments	1,001	(414)	760	(17)
(Loss) gain on change in fair value of equity investments	(38)	337	(23)	1,081
Income from discontinued operations, net of taxes	0	417	0	1,397
Loss on disposal of discontinued operations, net of taxes	$ 0	(1,172)	$ 0	(7,800)
Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss on disposal of discontinued operations, net of taxes					$ 1,300
Mendota and ARS | Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total revenues		16,727		68,319
Loss and loss adjustment expenses		(14,104)		(55,832)
Commissions and premium taxes		(713)		(7,101)
General and administrative expenses		(3,925)		(11,703)
Net investment income		240		674
Gain on change in fair value of equity investments		130		(4)
(Loss) gain on change in fair value of equity investments		(122)		(16)
Other income		2,184		7,060
Total other revenue (expenses), net		(16,310)		(66,922)
Income from discontinued operations before income tax benefit		417		1,397
Income tax benefit		0		0
Income from discontinued operations, net of taxes		417		1,397
Loss on disposal of discontinued operations before income tax expense		(1,172)		(7,800)
Income tax expense		0		0
Loss on disposal of discontinued operations, net of taxes		(1,172)		(7,800)
Total loss from discontinued operations, net of taxes		$ (755)		$ (6,403)