Schedule III Properties And Accumulated Depreciation (Summary Of Accumulated Depreciation And Amortization) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Schedule III Properties And Accumulated Depreciation [Abstract]
Balance, beginning of year	$ 900,044	$ 660,700	$ 459,521
Additions during period (depreciation and amortization expense)	305,973	239,344	201,190
Deductions during period (dispositions and write-off of tenant improvements)			(11)
Balance, end of year	$ 1,206,017	$ 900,044	$ 660,700