Stock Based Compensation (Performance Units Information) (Details) - Performance Units [Member] - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period for recognizing unrecognized compensation cost	1 year
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Shares, Outstanding at Beginning of Year	765,633
Shares, Granted	337,585
Shares, Vested	(655,201)
Shares, Canceled	(44,056)
Shares, Outstanding at End of Year	403,961	765,633
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Shares, Outstanding at Beginning of Year, Weighted Average Grant Date Fair Value	$ 36.86
Shares, Granted, Weighted Average Grant Date Fair Value	41.32	$ 38.94	$ 35.07
Shares, Vested, Weighted Average Grant Date Fair Value	36.82
Shares, Cancelled, Weighted Average Grant Date Fair Value	38.97
Shares, Outstanding at End of Year, Weighted Average Grant Date Fair Value	$ 40.42	$ 36.86
Shares, Outstanding at End of Year, Weighted Average Remaining Years Contractual Term	1 year 7 months 6 days
Shares, Outstanding at End of Year, Aggregate Intrinsic Value	$ 15,629,251