Income Taxes - Summary of Income Tax Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current Income Tax Expense:
Federal	$ 32,999	$ 41,946	$ 91,664
State	5,442	8,682	9,393
Current Income Tax Expense (Benefit), Total	38,441	50,628	101,057
Deferred Income Tax Expense (Benefit):
Federal	35,413	(3,314)	(35,941)
State	3,557	(3,843)	(822)
Deferred Income Tax Expense (Benefit), Total	38,970	(7,157)	(36,763)
INCOME TAXES	$ 77,411	$ 43,471	$ 64,294