Equity Transactions (Details) - Common Stock [Member] - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2016	Mar. 31, 2015	Aug. 31, 2013
Schedule of Equity Transactions [Line Items]
Stock Repurchase Program, Authorized Amount	$ 450.0		$ 200.0
Stock Repurchase, Additional Authorization		$ 250.0
Stock Repurchased During Period, Shares	0
Stock Repurchased and Retired Since Program Inception, shares	4,247,867
Stock Acquired and Retired Since Program Inception, Average Cost Per Share	$ 71.79
Stock Repurchased And Retired, Value	$ 304.9
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 145.1
Common Stock, Terms of Conversion	For each share of the Company’s stock repurchased, one of the Company’s Operating Partnership units was redeemed