Income Taxes - Provision (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current
Federal	$ 29,117	$ 19,309	$ 5,144
State	5,325	2,959	645
Total	34,442	22,268	5,789
Deferred
Federal	14,571	8,862	15,868
State	2,348	1,398	2,343
Total	16,919	10,260	18,211
Items charged or credited directly to stockholders' equity
Federal	1,218	(33)	1,091
State	192	(5)	166
Total	1,410	(38)	1,257
Income tax expense	$ 52,771	$ 32,490	$ 25,257