Stock-Based Compensation (Details Textual) (USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Number of common stock shares which are authorized to issue awards	24.3
Common Stock, Capital Shares Reserved for Future Issuance	20.5
Shares available for future issuance	3.8
Payout Percentage	100.00%
Undistributed performance share units	0.5
Weighted-average grant date fair value of undistributed performance share units	$ 47.81
Undistributed and vested performance share units	0.2
Maximum [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Potential increase for payout percentage	200.00%
Performance Shares [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Award service period	3 years
Payout Percentage	86.90%	52.50%	0.00%
Total unrecognized compensation cost	$ 19.8
Weighted average period of recognition	2 years 1 month 24 days
Estimated forfeiture rate	16.40%
Restricted Stock Units (RSUs) [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Award service period	3 years
Total unrecognized compensation cost	13.6
Weighted average period of recognition	2 years 3 months 18 days
Estimated forfeiture rate	17.50%
Stock Appreciation Rights [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Award expiration period	7 years
Vesting percentage	33.33%
Total unrecognized compensation cost	$ 9.2
Weighted average period of recognition	2 years 3 months 24 days
Estimated forfeiture rate	16.00%