Description of Business and Accounting Policies (Details) $ / shares in Units, shares in Millions	3 Months Ended				9 Months Ended		12 Months Ended
	Sep. 30, 2015 USD ($) $ / shares shares	Jun. 30, 2015 USD ($) $ / shares shares	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($) $ / shares shares	Sep. 30, 2015 USD ($) shares	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Number of Operating Segments							3
Proceeds from Sale of Intangible Assets			$ 194,400,000		$ 0	$ 194,400,000
Equity Method Investment Sold, Partnership Units | shares	6.0	14.3		16.0
Sale of Partnership Units, Price Per Unit | $ / shares	$ 28.41	$ 29.88		$ 22.26
Proceeds from Sale of Equity Method Investments	$ 170,300,000	$ 426,000,000		$ 355,900,000	$ 596,300,000	355,900,000
Total ownership interests in Equity Method Investee, Percentage	11.00%				11.00%
Investment owned in CyrusOne Inc., Balance, Shares | shares	1.9				1.9
Investment owned in CyrusOne LP, Balance, Partnership Units | shares	6.3				6.3
Number of customers, exceeds 10% of total accounts receivable	1				1
Accounts Receivable from customers greater than 10%, percentage	$ 0.22				$ 0.22		$ 0.26
Revenue from customers greater than 10%, percentage	0.12		0.18		0.12	0.16
Dividends received from CyrusOne	$ 4,500,000		$ 6,000,000		$ 19,500,000	$ 22,400,000
Payments to Acquire Equity Method Investments				$ 5,500,000