Income Taxes - Schedule of Effective Rate Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Federal income tax expense at statutory rate	$ 15,414	$ 116,757	$ 112,326
Federal income tax expense at statutory rate, percent	35.00%	21.00%	21.00%
REIT income not subject to federal income tax	$ (14,897)	$ (115,395)	$ (111,035)
REIT income not subject to federal income tax, percent	(33.80%)	(20.80%)	(20.80%)
Pre-tax gain attributable to taxable subsidiaries	$ 517	$ 1,362	$ 1,291
Pre-tax gain attributable to taxable subsidiaries, percent	1.20%	0.30%	0.20%
State income taxes, net of federal benefits	$ 5	$ 542	$ 187
State income taxes, net of federal benefits, percent	0.00%	0.10%	0.00%
Non-deductible expenses and other	$ 0	$ (199)	$ (37)
Non-deductible expenses and other, percent	0.00%	0.00%	0.00%
Impact of Tax Reform on deferred tax liability	$ (2,423)	$ 0	$ 0
Impact of Tax Reform on deferred tax liability, percent	(5.50%)	0.00%	0.00%
Income tax expense (benefit)	$ (1,901)	$ 1,705	$ 1,441
Income tax expense (benefit), percent	(4.30%)	0.30%	0.20%