Related Party Transactions (Details) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Lease expiration, date			2026
Increase to rental revenues	$ 202,806,000	$ 156,831,000	$ 399,601,000	$ 308,138,000
Deferred rent	218,318,000		218,318,000		190,067,000
Deferred leasing cost	21,821,000		21,821,000		22,825,000
Deferred rent and unamortized deferred leasing costs	28,300,000		28,300,000		21,000,000
Minimum [Member]
Lease expiration, date			2013
Maximum [Member]
Lease expiration, date			2025
Tel(x) [Member]
Number of leases agreement			10
Increase to rental revenues	10,700,000	5,800,000	19,500,000	10,900,000
Square foot of net rentable space			254,314		202,987
Lease agreements			39		31
"Percentage rent" Lease revenue earned	600,000	400,000	700,000	400,000
SoftLayer [Member]
Number of leases agreement			7
Increase to rental revenues	$ 4,600,000	$ 400,000	$ 6,900,000	$ 400,000
Number of leases agreement for the current period			6
Number of leases agreement for future period			1