Stockholders' Equity - Changes by Component (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 1,814,789	$ 1,078,350	$ 257,881
Cumulative credit risk adjustment	0	(9,211)	0
Ending balance	1,541,472	1,814,789	1,078,350
(Loss) gain on extinguishment of debt	(12,437)	104	(55,360)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(1,950)	(1,845)	1,484
Cumulative credit risk adjustment		(9,211)
Change in net unrealized gain (loss)	271	4,783	(3,329)
Amounts reclassified to net income		4,323
Other comprehensive income (loss)	271	9,106
Ending balance	(1,679)	(1,950)	(1,845)
Foreign currency translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(1,950)	(553)	2,213
Cumulative credit risk adjustment		0
Change in net unrealized gain (loss)	271	(1,397)	(2,766)
Amounts reclassified to net income		0
Other comprehensive income (loss)	271	(1,397)
Ending balance	(1,679)	(1,950)	(553)
Unrealized loss on investment securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	0	(1,292)	(729)
Cumulative credit risk adjustment		0
Change in net unrealized gain (loss)	0	(1,510)	(563)
Amounts reclassified to net income		2,802
Other comprehensive income (loss)	0	1,292
Ending balance	0	0	(1,292)
Other-than-temporary impairment losses		1,800
Realized losses on investments		1,000
(Loss) gain on extinguishment of debt		1,500
Redemption Note
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	0	0	0
Cumulative credit risk adjustment		(9,211)
Change in net unrealized gain (loss)	0	7,690	0
Amounts reclassified to net income		1,521
Other comprehensive income (loss)	0	9,211
Ending balance	$ 0	$ 0	$ 0