Summary Of Significant Accounting Policies (Narrative) (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013 segment	Dec. 31, 2012	Dec. 31, 2011
Summary Of Significant Accounting Policies [Line Items]
Period in which short-term investment become cash equivalents									90 days
Interest capitalized									$ 26,300,000	$ 21,500,000	$ 17,900,000
Capitlization threshold for operating expenditures									10,000
Incremental amounts capitalized that would have been recorded as rental operating expense under previous policies									9,500,000
Compensation costs, leasing and construction activities									37,600,000	31,600,000	24,700,000
Cash flows from capitalized leasing costs									57,500,000	40,100,000	28,200,000
Ineffective portion of cash flow hedges									0	0	0
Asset retirement obligations	1,700,000				1,700,000				1,700,000	1,700,000
Assets or liabilities for uncertain tax positions	0				0				0	0
Interest or penalties from uncertain tax positions									0	0	0
Number of reportable segments									1
Total operating revenues	380,931,000	379,456,000	363,502,000	358,370,000	349,736,000	342,479,000	303,704,000	283,148,000	1,482,259,000	1,279,067,000	1,062,710,000
Lease term extension									5 years
United States [Member]
Summary Of Significant Accounting Policies [Line Items]
Total operating revenues									1,100,000,000	1,100,000,000	946,000,000
Long-lived assets	5,600,000,000				5,000,000,000				5,600,000,000	5,000,000,000	4,300,000,000
Outside The United States [Member]
Summary Of Significant Accounting Policies [Line Items]
Total operating revenues									349,100,000	228,900,000	116,700,000
Long-lived assets	2,700,000,000				2,500,000,000				2,700,000,000	2,500,000,000	1,000,000,000
United Kingdom [Member]
Summary Of Significant Accounting Policies [Line Items]
Total operating revenues									197,000,000	117,200,000	43,600,000
Long-lived assets	$ 1,800,000,000				$ 1,700,000,000				$ 1,800,000,000	$ 1,700,000,000	$ 356,000,000
Sales [Member] | United Kingdom [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration risk									13.30%	9.20%	4.10%
Long-Lived Assets [Member] | United Kingdom [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration risk									21.10%	22.30%	6.80%
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Building and improvements, useful life									5 years
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Building and improvements, useful life									39 years