Stockholders' Equity (Restricted Stock and Deferred Issuance Restricted Stock) (Details) (Restricted Stock and Deferred Issuance Restricted Stock [Member], USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012
Restricted Stock and Deferred Issuance Restricted Stock [Member]
Restricted Stock and Deferred Issuance Restricted Stock [Roll Forward]
Number of Shares, Unvested, Beginning Balance	62
Number of Shares, Granted	3
Number of Shares, Vested and exercised	(3)
Number of Shares, Forfeited	(1)
Number of Shares, Unvested, Ending Balance	61
Weighted Average Grant Date Fair Value, Unvested, Beginning Balance	$ 54.35
Weighted Average Grant Date Fair Value, Granted	$ 61.86
Weighted Average Grant Date Fair Value, Vested and exercised	$ 51.17
Weighted Average Grant Date Fair Value, Forfeited	$ 53.26
Weighted Average Grant Date Fair Value, Unvested, Ending Balance	$ 54.82