Shareholders' Equity and Partners' Capital (Common Stock Sold) (Details) (Common Stock [Member], USD $)	3 Months Ended		12 Months Ended
	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2013	Mar. 01, 2013
Common Stock [Member]
Class of Stock [Line Items]
Common stock offering, maximum aggregate price				$ 300,000,000
Common stock offering, maximum commission fee (percent)				2.00%
Number of Shares Settled	6,530,193	1,889,105	8,419,298
Gross Proceeds	167,034,000	44,459,000	211,493,000
Net Proceeds	165,692,000	43,904,000	209,596,000
Weighted-average Sales Price	$ 25.58	$ 23.53	$ 25.12
Common stock offering, maximum remaining aggregate price			$ 88,507,000