Employee Benefit Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Employee Benefit Plan [Abstract]
Maximum contribution % of eligible pre-tax compensation allowed to participants of defined contribution plan	50.00%
Our contributions match	$ 7.6	$ 7.2	$ 6.7
Our matching cash contributions represents this % of contributions made by participants of defined contribution plan	50.00%
Maximum employer contribution match % (of total eligible compensation) to each participant of defined contribution plan	6.00%
Our common stock % in total plan assets	3.60%	4.50%