Notes and Bonds Payable (Details 6) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2011	Dec. 31, 2010
Future maturities of the Company's notes and bonds payable
Principal Maturities	$ 1,262,760
Net Accretion/Amortization	(11,131)
Notes and Bonds Payable	1,251,629	1,407,855
%	100.00%
2011 (remaining) [Member]
Future maturities of the Company's notes and bonds payable
Principal Maturities	1,665
Net Accretion/Amortization	(720)
Notes and Bonds Payable	945
%	0.10%
2012 [Member]
Future maturities of the Company's notes and bonds payable
Principal Maturities	126,491
Net Accretion/Amortization	(1,508)
Notes and Bonds Payable	124,983
%	10.00%
2013 [Member]
Future maturities of the Company's notes and bonds payable
Principal Maturities	18,284
Net Accretion/Amortization	(1,738)
Notes and Bonds Payable	16,546
%	1.30%
2014 [Member]
Future maturities of the Company's notes and bonds payable
Principal Maturities	268,460
Net Accretion/Amortization	(1,786)
Notes and Bonds Payable	266,674
%	21.30%
2015 [Member]
Future maturities of the Company's notes and bonds payable
Principal Maturities	32,632
Net Accretion/Amortization	(1,443)
Notes and Bonds Payable	31,189
%	2.50%
2016 and thereafter [Member]
Future maturities of the Company's notes and bonds payable
Principal Maturities	815,228
Net Accretion/Amortization	(3,936)
Notes and Bonds Payable	$ 811,292
%	64.80%