Income Taxes - Summary of Income Tax Expense Benefit (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current
Federal	$ 9,078	$ 667	$ 653
State	0	2	30
Deferred
Federal	7,018	32,791	12,163
State	4,163	2,876	2,043
Total income tax provision	$ 20,259	$ 36,336	$ 14,889