Stock-Based Compensation (Restricted Stock) (Details) (Restricted Stock [Member], USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period (in years)	4 years
Total fair value of vested restricted stock awards	$ 6.8		$ 5.8		$ 5.5
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested, Shares, beginning balance	300,000
Nonvested, Weighted-Average Grant Date Fair Value, beginning balance	$ 27.81
Granted, Shares	100,000	[1]
Granted, Weighted-Average Grant Date Fair Value	$ 43.45	[1]	$ 34.31	[1]	$ 32.50	[1]
Vested, Shares	(100,000)
Vested, Weighted-Average Grant Date Fair Value	$ 24.33
Forfeited, Shares	0
Forfeited, Weighted-Average Grant Date Fair Value	$ 0.00
Nonvested, Shares, ending balance	300,000		300,000
Nonvested, Weighted-Average Grant Date Fair Value, ending balance	$ 35.76		$ 27.81
Annual Employee Grant, 2013 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized	100,000

[1] The restricted stock awards granted during 2013 are related to our employee annual restricted stock award grant in March 2013.