Stock Based Compensation (Performance Units Information) (Details) - Performance Units [Member] - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
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	403,961
Shares, Granted	319,718
Shares, Vested	(301,554)
Shares, Canceled	(28,313)
Shares, Outstanding at End of Year	393,812	403,961
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	$ 40.42
Shares, Granted, Weighted Average Grant Date Fair Value	45.97	$ 41.32	$ 38.94
Shares, Vested, Weighted Average Grant Date Fair Value	41.22
Shares, Cancelled, Weighted Average Grant Date Fair Value	42.04
Shares, Outstanding at End of Year, Weighted Average Grant Date Fair Value	$ 44.20	$ 40.42
Shares, Outstanding at End of Year, Weighted Average Remaining Years Contractual Term	1 year 220 days
Shares, Outstanding at End of Year, Aggregate Intrinsic Value	$ 17,280,471