Management Compensation Plans (Schedule of Summary of Changes in Time-based RSUs Outstanding) (Details) (USD $)	3 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2013
Employee [Member] | Time Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
As of beginning of period, number of units		431,000
Granted, number of units		25,000
Vested, number of units		(211,000)
Forfeited, number of units		(20,000)
As of end of period, number of units		225,000	[1]
As of beginning of period, weighted average fair value		$ 34.41
Granted, weighted average fair value		$ 49.56
Vested, weighted average fair value		$ 33.79
Forfeited, weighted average fair value		$ 30.39
As of end of period, weighted average fair value		$ 37.02
Director [Member] | Time Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
As of beginning of period, number of units		16,000
Granted, number of units		16,000
Vested, number of units		(16,000)
Forfeited, number of units		0
As of end of period, number of units		16,000
As of beginning of period, weighted average fair value		$ 47.48
Granted, weighted average fair value		$ 48.51
Vested, weighted average fair value		$ 47.48
Forfeited, weighted average fair value		$ 0
As of end of period, weighted average fair value		$ 48.51
Chief Executive Officer [Member] | Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, number of units		66,108
Vested, number of units	(22,013)	(22,013)

[1] Includes 66,108 of restricted stock awards granted to the Company's Chief Executive Officer on April 5, 2012, of which 22,013 and 22,013 vested on October 1, 2012 and April 5, 2013, respectively.