Acquisition (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012 years	Jan. 31, 2012
Business Acquisition [Line Items]
Average amortization period, long-term prepaid rent	29.4
Wireless Capital Partners, LLC [Member]
Business Acquisition [Line Items]
Business acquisitions, purchase price allocation, current assets, restricted cash		$ 39.2
Ground lease related assets		2,300
Business acquisition, purchase price allocation, non-current liabilities, long-term debt assumed	336.3
Business acquisition, cost of acquired entity, purchase price		214.7
Long-term prepaid rent [Member] | Wireless Capital Partners, LLC [Member]
Business Acquisition [Line Items]
Business acqusition, purchase price allocation, non-current assets, prepaid rent		$ 318
Average amortization period, long-term prepaid rent	38