Share-Based Compensation (Details 1) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011
Time-Based Restricted Stock Units (RSUs) [Member]
Summary of Time-Based RSUs
Outstanding at January 1, 2012, Vested RSUs and Total RSUs	842,675
Granted, Shares	196,033	[1]
Vested, Shares	0
Issuance of dividend equivalents	7,552	[2]
Canceled	(4,181)	[3]
Outstanding as of March 31, 2012, Vested RSUs and Total RSUs	1,042,079
Summary of Granted and Vested Time-Based Restricted Stock Units
Granted, Shares	196,033	[1]
Vested, Shares	0
Nonvested Restricted Stock Units RSU [Member]
Summary of Time-Based RSUs
Outstanding at January 1, 2012 , Shares	147,961
Outstanding at January 1, 2012, Weighted Average Grant Date Fair Value Per Share	$ 32.18
Granted, Shares	196,033	[1]	97,597
Granted, Weighted Average Grant Date Fair Value Per Share	$ 44.29		$ 37.76
Vested, Shares	(48,864)		(10,079)
Vested, Weighted Average Grant Date Fair Value Per Share	$ 36.20
Outstanding as of March 31, 2012, Shares	295,130
Outstanding as of March 31, 2012, Weighted Average Grant Date Fair Value Per Share	$ 39.56
Summary of Granted and Vested Time-Based Restricted Stock Units
Granted, Shares	196,033	[1]	97,597
Granted, Weighted Average Grant Date Fair Value Per Share	$ 44.29		$ 37.76
Vested, Shares	(48,864)		(10,079)
Vested shares, total fair value	$ 1,961	[4]	$ 382	[4]
Vested Restricted Stock Units RSU [Member]
Summary of Time-Based RSUs
Outstanding at January 1, 2012, Vested RSUs and Total RSUs	694,714
Granted, Shares	0
Vested, Shares	48,864
Issuance of dividend equivalents	7,552	[2]
Canceled	(4,181)	[3]
Outstanding as of March 31, 2012, Vested RSUs and Total RSUs	746,949
Summary of Granted and Vested Time-Based Restricted Stock Units
Granted, Shares	0
Vested, Shares	48,864

[1] Includes 103,239 RSUs issued to the Company's Chief Executive Officer, as described above.

[2] RSUs issued as dividend equivalents are vested upon issuance.

[3] We accept the return of RSUs, at the current quoted closing share price of the Company's common stock, to satisfy minimum statutory tax-withholding requirements related to either RSUs that have vested or RSU dividend equivalents in accordance with the terms of the 2006 Plan.

[4] Total fair value of RSUs vested was calculated based on the quoted closing share price of the Company's common stock on the NYSE on the day of vesting.