Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Taxes [Line Items]
Deferred tax liability increased due to change in taxable status		$ 13,181
Statutory federal income tax rate	35.00%	35.00%	35.00%	35.00%
Deferred income tax expense related to unrealized gain on available for sale securities	$ 274	$ 13,193	$ 8,226	$ 14,239
C Corporation
Income Taxes [Line Items]
Deferred tax liability increased due to change in taxable status		13,181		$ 13,181
Deferred income tax expense related to unrealized gain on available for sale securities		$ 2,955