Employee Benefit Plan (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Employee Benefit Plan (Details) [Abstract]
Maximum contribution % of eligible pre-tax compensation allowed to participants of defined contribution plan	50.00%
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	2.00%
Our common stock % in total plan assets	6.80%	10.00%	12.00%
Our contributions match	$ 6.6	$ 5.3	$ 5.8