Liability for Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Accrued Income Taxes [Abstract]
Unrecognized Tax Benefits, Interest on Income Taxes Expense	$ 136	$ 376	$ 1,807
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at	3,041	7,450
Additions based on tax positions related to the current year	0	328
Additions for tax positions of prior years	136	376
Reductions for tax positions of prior years	(2,561)	(5,113)
Settlements & other, net	(49)	0
Balance at	567	3,041	7,450
Reversal of income tax liability	2,561	5,113	42,472
Tax Adjustments, Settlements, and Unusual Provisions	0	3,162	37,307
Interest Expense Benefit Due To Lapse Of Applicable Statute Of Limitations	$ 2,561	$ 1,951
Taxable Reit Subsidiary [Member]
Income Tax Contingency [Line Items]
Open Tax Years by Major Tax Jurisdiction	2005 through 2010
Real Estate Investment Trust [Member]
Income Tax Contingency [Line Items]
Open Tax Years by Major Tax Jurisdiction	2008 through 2010