401(k) Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Compensation and Retirement Disclosure [Abstract]
Period to become eligible to participate in 401(k) Plan	1 month
Matching contributions to voluntary retirement plan	$ 2.5	$ 2.1	$ 1.7