Shareholders' Equity - Reclassified out of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized (losses) gains on investment									$ (1,529)	$ 12,222	$ 6,774
(Loss) income from continuing operations before income taxes									(449,851)	(154,406)	79,473
Income tax benefit									(441)	6,757	(413)
Net (loss) income	$ (269,196)	$ (300,232)	$ 2,680	$ 22,343	$ (124,857)	$ (55,054)	$ (16,335)	$ 26,501	(544,405)	(169,745)	48,138
Unrealized (losses) gains on AFS securities | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net realized (losses) gains on investment									(21,243)	1,816	(576)
Net impairment losses recognized in earnings									(5,832)	0	0
(Loss) income from continuing operations before income taxes									(27,075)	1,816	(576)
Income tax benefit									0	0	0
Net (loss) income									$ (27,075)	$ 1,816	$ (576)