Stock Based Compensation (Performance Units Information) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Performance Share Risk Free Rate Assumption	1.36%	2.47%	2.36%
Performance Share Volatility Rate Assumption	15.00%	16.74%	17.57%
Performance Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average period for recognizing unrecognized compensation cost	1 year 8 months 12 days
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	334,515
Shares, Granted	447,815
Shares, Vested	(285,977)
Shares, Canceled	(20,512)
Shares, Outstanding at End of Year	475,841	334,515
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	$ 59.30
Shares, Granted, Weighted Average Grant Date Fair Value	51.79	$ 62.17	$ 54.95
Shares, Vested, Weighted Average Grant Date Fair Value	54.96
Shares, Cancelled, Weighted Average Grant Date Fair Value	58.37
Shares, Outstanding at End of Year, Weighted Average Grant Date Fair Value	$ 54.88	$ 59.30
Shares, Outstanding at End of Year, Weighted Average Remaining Years Contractual Term	1 year 8 months 12 days
Shares, Outstanding at End of Year, Aggregate Intrinsic Value	$ 27,741,530
Performance Units [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Options vesting period	3 years