Share-Based Compensation (Details 2) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	62,137		68,727		3,239
Granted, Weighted Average Grant Date Fair Value (in dollars per share)	$ 41.84		$ 37.83		$ 30.88
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period	(50,862)		(34,793)		(41,680)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Total Fair Value	$ 2,110		$ 1,334		$ 1,398
Nonvested Restricted Stock Units R S U [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (in shares)	204,829		107,673		159,606
Granted, Weighted Average Grant Date Fair Value (in dollars per share)	$ 44.34		$ 37.94		$ 30.24
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period	(73,688)		(85,466)		(303,146)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Total Fair Value	$ 3,118	[1]	$ 3,273	[1]	$ 10,936	[1]

[1] 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.