Employee Benefits (Details Textual) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Employee Benefits (Textual) [Abstract]
Maximum percentage of a participant's eligible compensation that a participating may elect to contribute, on a tax-deferred annually to the plan (as a percent) 50.00%	80.00%
Percentage of matching contribution made by company, of first 6% of participating employees contributions (as a percent)	50.00%
Percentage of participating employees contribution, matched 100% (as a percent)	6.00%
Employer contribution	$ 8.5	$ 7.9	$ 8.4
Deferred gains or (losses) of investment	$ 4.3	$ (0.4)	$ 3.7