Fair Value Measurements and Disclosures (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012		Mar. 31, 2011	Dec. 31, 2011
Assets and Liabilities Reported at Fair Value
Marketable securities	$ 6,459			$ 5,691
Fair value adjustment of marketable securities and deferred compensation plan liability
Net gain on marketable securities	435		187
(Increase) to compensation cost	(435)		(187)
Fair Value (Level 1) [Member]
Assets and Liabilities Reported at Fair Value
Marketable securities	6,459	[1],[2]		5,691	[1],[2]
Deferred compensation plan liability	$ 6,364	[1],[3]		$ 5,597	[1],[3]

[1] Based on quoted prices in active markets for identical securities.

[2] The marketable securities are held in a limited rabbi trust.

[3] The deferred compensation plan liability is reported on our consolidated balance sheets in accounts payable, accrued expenses, and other liabilities.