Stock-Based Compensation Plans (Summary Of Restricted Stock Units Activity) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, Nonvested as of December 31	348,450		521,100		648,250
Nonvested, Granted	329,160	[1]	37,500	[2]	32,500	[3]
Vested	(143,150)	[4]	(158,150)	[5]	(149,650)	[6]
Nonvested, Forfeited	(8,500)		(52,000)		(10,000)
Outstanding, Nonvested as of December 31	525,960		348,450		521,100
Weighted Average Grant-Date Fair Value Per Share, Nonvested, Outstanding as of December 31	$ 24.06		$ 19.99		$ 19.35
Weighted Average Grant-Date Fair Value Per Share, Nonvested, Granted	$ 105.74	[1]	$ 63.73	[2]	$ 39.89	[3]
Weighted Average Grant-Date Fair Value Per Share, Nonvested, Vested	$ 21.48	[4]	$ 20.99	[5]	$ 20.24	[6]
Weighted Average Grant-Date Fair Value Per Share, Nonvested, Forfeited	$ 15.80		$ 20.18		$ 39.89
Weighted Average Grant-Date Fair Value Per Share, Nonvested, Outstanding as of September 30	$ 76.01		$ 24.06		$ 19.99
Outstanding, Vested as of December 31	427,800		269,650		120,000
Vested	143,150	[4]	158,150	[5]	149,650	[6]
Outstanding, Vested as of December31	570,950		427,800		269,650
Weighted Average Grant-Date Fair Value Per Share, Vested, Outstanding as of December 31	$ 22.14		$ 22.94		$ 26.30
Weighted Average Grant-Date Fair Value Per Share, Vested, Outstanding as of December 31	$ 21.97		$ 22.14		$ 22.94
Outstanding, Total as of December 31	776,250		790,750		768,250
Total, Granted	329,160	[1]	37,500	[2]	32,500	[3]
Total, Forfeited	(8,500)		(52,000)		(10,000)
Outstanding, Total as of December 31	1,096,910		776,250		790,750
February 22, 2018 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Distribution date of vested restricted stock units			5,000
February 18, 2019 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Distribution date of vested restricted stock units	3,000		32,500
February 22, 2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Distribution date of vested restricted stock units	60,000		60,000		60,000
February 22, 2016 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Distribution date of vested restricted stock units	76,650		89,650		89,650
February 22, 2017 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Distribution date of vested restricted stock units	6,500		8,500
February 19, 2020 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Distribution date of vested restricted stock units	16,160
December 31, 2022, 2023, 2024, 2025, and 2026 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Distribution date of vested restricted stock units	310,000

[1] The distribution date of vested restricted stock units is February 18, 2019 for 3,000 restricted stock units and February 19, 2020 for 16,160 restricted stock units.  For 310,000 restricted stock units, the vested restricted stock units will be distributed in equal installments on December 31, 2022, 2023, 2024, 2025 and 2026.

[2] The distribution date of vested restricted stock units is February 22, 2018 for 5,000 restricted stock units and February 18, 2019 for 32,500 restricted stock units.

[3] The distribution date of vested restricted stock units is February 22, 2017.

[4] The distribution date of vested restricted stock units is February 22, 2014 for 60,000 restricted stock units, February 22, 2016 for 76,650 restricted stock units and February 22, 2017 for 6,500 restricted stock units.

[5] The distribution date of vested restricted stock units is February 22, 2014 for 60,000 restricted stock units and February 22, 2016 for 89,650 restricted stock units and February 22, 2017 for 8,500 restricted stock units.

[6] The distribution date of vested restricted stock units is February 22, 2014 for 60,000 restricted stock units and February 22, 2016 for 89,650 restricted stock units.