Stock-Based Compensation (Schedule of Grant Date Fair Value of Restricted Stock) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Time-Vested [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Average grant-date fair value of restricted stock awarded (in usd per share)	$ 53.17	$ 45.62	$ 43.19
Performance-based [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Average grant-date fair value of restricted stock awarded (in usd per share)	49.50	48.31	36.75
Deferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Average grant-date fair value of restricted stock awarded (in usd per share)	$ 55.19	$ 49.49	$ 43.79