Share-Based Compensation (Details 1) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2012		Sep. 30, 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	204,829	[1]
Vested, Shares	0
Settled (in shares)	(5,207)	[2]
Issuance of dividend equivalents	21,262	[3]
Canceled	(7,054)	[4]
Outstanding as of June 30, 2012, Vested RSUs and Total RSUs	1,056,505
Summary of Granted and Vested Time-Based Restricted Stock Units
Granted, Shares	204,829	[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	204,829	[1]	107,673
Granted, Weighted Average Grant Date Fair Value Per Share	$ 44.34		$ 37.94
Vested, Shares	(58,940)		(23,035)
Vested, Weighted Average Grant Date Fair Value Per Share	$ 36.80
Outstanding as of June 30, 2012, Shares	293,850
Outstanding as of June 30, 2012, Weighted Average Grant Date Fair Value Per Share	$ 41.57
Summary of Granted and Vested Time-Based Restricted Stock Units
Granted, Shares	204,829	[1]	107,673
Granted, Weighted Average Grant Date Fair Value Per Share	$ 44.34		$ 37.94
Vested, Shares	(58,940)		(23,035)
Vested shares, total fair value	$ 2,420	[5]	$ 897	[5]
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	58,940
Settled (in shares)	(5,207)	[2]
Issuance of dividend equivalents	21,262	[3]
Canceled	(7,054)	[4]
Outstanding as of June 30, 2012, Vested RSUs and Total RSUs	762,655
Summary of Granted and Vested Time-Based Restricted Stock Units
Granted, Shares	0
Vested, Shares	58,940

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

[2] In August 2012, certain vested RSUs were settled in shares of the Company's common stock.

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

[4] 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 the issuance, vesting or settlement of RSUs in accordance with the terms of the 2006 Plan.

[5] 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.