Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Current tax expense	$ 7,355	$ 6,125	$ 4,279
Deferred tax expense	724	882	1,741
Deferred tax asset adjustment for tax rate change	2,747	0	0
Total income tax expense	$ 10,826	$ 7,007	$ 6,020