Equity (Summary of Restricted Stock and Goal-Based Stock Activity) (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested beginning, Shares	1,065	1,007	1,085
Granted, Shares	302	354	312
Vested, Shares	(510)	(278)	(356)
Cancelled and forfeited, Shares	(2)	(18)	(34)
Nonvested ending, Shares	855	1,065	1,007
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Nonvested beginning, Weighted Average Grant Date Fair Value	$ 56.74	$ 49.35	$ 44.46
Granted, Weighted Average Grant Date Fair Value	73.26	67.98	54.70
Vested, Weighted Average Grant Date Fair Value	50.71	44.50	39.00
Cancelled and forfeited, Weighted Average Grant Date Fair Value	62.62	53.61	51.11
Nonvested ending, Weighted Average Grant Date Fair Value	$ 66.16	$ 56.74	$ 49.35
Goal-Based Stock
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested beginning, Shares	17	5	4
Granted, Shares	14	13	4
Vested, Shares	(7)	(1)	(2)
Cancelled and forfeited, Shares			(1)
Nonvested ending, Shares	24	17	5
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward]
Nonvested beginning, Weighted Average Grant Date Fair Value	$ 65.15	$ 53.85	$ 45.60
Granted, Weighted Average Grant Date Fair Value	72.72	68.83	54.17
Vested, Weighted Average Grant Date Fair Value	56.22	52.48	43.54
Cancelled and forfeited, Weighted Average Grant Date Fair Value			43.54
Nonvested ending, Weighted Average Grant Date Fair Value	$ 72.27	$ 65.15	$ 53.85