Senior Unsecured Notes and Secured Debt (Details) In Thousands, unless otherwise specified			9 Months Ended
	Sep. 30, 2012 USD ($)	Dec. 31, 2011 USD ($)	Sep. 30, 2012 Senior Unsecured Notes [Member] USD ($)		Sep. 30, 2012 Secured Debt [Member] USD ($)		Sep. 30, 2012 Term Loan [Member] USD ($)	Jul. 30, 2012 Term Loan [Member] CAD
Principal payments due on debt obligations
2012	$ 9,914		$ 0	[1],[2]	$ 9,914	[1],[3]
2013	521,368		300,000	[1],[2]	221,368	[1],[3]
2014	201,848		0	[1],[2]	201,848	[1],[3]
2015	725,438		504,143	[1],[2],[4]	221,295	[1],[3]
2016	1,018,507		700,000	[1],[2]	318,507	[1],[3]
Thereafter	4,771,992		3,444,403	[1],[2]	1,327,589	[1],[3]
Totals	7,249,067		4,948,546	[1],[2]	2,300,521	[1],[3]
Senior Unsecured Notes and Secured Debt (Textual) [Abstract]
Notes, annual stated interest rates, Minimum			2.70%		1.20%
Notes, annual stated interest rates, Maximum			6.50%		8.00%
Canadian Term Loan	4,921,712	4,434,107					254,143	250,000
Additional Senior Unsecured Notes and Secured Debt (Textual) [Abstract]
Secured debt	2,314,717	2,112,649
Carrying values of properties securing the debt	$ 5,083,684

[1] (1) Amounts represent principal amounts due and do not include unamortized premiums/discounts or other fair value adjustments as reflected on the balance sheet.

[2] (2) Annual interest rates range from 3.0% to 6.5%, excluding the Canadian denominated unsecured term loan discussed in footnote 4.

[3] (3) Annual interest rates range from 1.2% to 8.0%. Carrying value of the properties securing the debt totaled $5,083,684,000 at September 30, 2012.

[4] (4) On July 30, 2012, we completed funding on a $250,000,000 Canadian denominated unsecured term loan (approximately $254,143,000 USD at exchange rates on September 30, 2012). The loan is coterminous with the unsecured revolving credit facility and matures July 27, 2015 (with an option to extend for an additional year at our discretion) and bears interest at the Canadian Dealer Offered Rate plus 145 basis points (2.65% at September 30, 2012).