Share-Based Compensation and Benefit Plans (Summary of Restricted Stock) (Details) - Restricted stock [Member] - $ / shares shares in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share-Based Compensation and Benefit Plans
Restricted stock granted during period, weighted-average grant date fair value		$ 208.56	$ 147.23	$ 102.63
Employee [Member]
Share-Based Compensation and Benefit Plans
Non-vested restricted stock at beginning of the year, weighted-average grant date fair value		123.68
Restricted stock granted during period, weighted-average grant date fair value		192.65
Restricted stock vested during the period, weighted-average grant date fair value	[1]	87.59
Restricted stock forfeited during the period, weighted-average grant date fair value		129.93
Non-vested restricted stock at the end of the year, weighted-average grant date fair value		$ 128.27	$ 123.68
Employee [Member] | Performance shares [Member]
Share-Based Compensation and Benefit Plans
Non-vested restricted stock beginning balance, shares		16
Restricted stock granted during the period, shares		2
Restricted stock vested during the period, shares	[1]	(10)
Restricted stock forfeited during the period, shares		(1)
Non-vested restricted stock ending balance, shares		7	16
Director [Member]
Share-Based Compensation and Benefit Plans
Non-vested restricted stock at beginning of the year, weighted-average grant date fair value		$ 124.44
Restricted stock granted during period, weighted-average grant date fair value		217.38
Restricted stock vested during the period, weighted-average grant date fair value		117.31
Restricted stock forfeited during the period, weighted-average grant date fair value		0.00
Non-vested restricted stock at the end of the year, weighted-average grant date fair value		$ 167.73	$ 124.44
Director [Member] | Performance shares [Member]
Share-Based Compensation and Benefit Plans
Non-vested restricted stock beginning balance, shares		8
Restricted stock granted during the period, shares		3
Restricted stock vested during the period, shares		(4)
Restricted stock forfeited during the period, shares		0
Non-vested restricted stock ending balance, shares		7	8

[1] Includes four thousand shares withheld to cover employees' taxes upon vesting.