Fair Value of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Jan. 19, 2011
Carrying amount and fair value of financial instruments
Marketable securities	$ 24,287	$ 28,235
Secured notes payable	964,538	943,479	342,000
Carrying Value [Member]
Carrying amount and fair value of financial instruments
Marketable securities	24,287	28,235
Secured notes payable	964,538	943,479
Deferred compensation liability	571	520
Fair Value [Member]
Carrying amount and fair value of financial instruments
Marketable securities	24,287	28,235
Secured notes payable	987,944	974,273
Deferred compensation liability	$ 571	$ 520