Employee Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Contribution Plan Disclosure [Line Items]
Contributions made to 401(k)	$ 2.3	$ 2.2	$ 2.4
First Tier of Deferral
Defined Contribution Plan Disclosure [Line Items]
Percent of gross pay	100.00%
Percent of eligible deferral	4.00%
Second Tier of Deferral
Defined Contribution Plan Disclosure [Line Items]
Percent of gross pay	50.00%
Percent of eligible deferral	2.00%