Fair Value Measurements and Disclosures (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Assets and Liabilities Reported at Fair Value
Marketable securities	$ 7,435		$ 5,691
Fair value adjustment of marketable securities and deferred compensation plan liability
Net loss (gain) on marketable securities	723		(153)		435
Fair Value (Level 1) [Member]
Assets and Liabilities Reported at Fair Value
Marketable securities	7,435	[1],[2]	5,691	[1],[2]
Deferred compensation plan liability	$ 7,339		$ 5,597

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

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