Capital and Financing Transactions Interest Rate Swaps (Details) (USD $)			6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		0 Months Ended	6 Months Ended		6 Months Ended		6 Months Ended		0 Months Ended	6 Months Ended		6 Months Ended				6 Months Ended						0 Months Ended	6 Months Ended		0 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 Swap 1 [Member] Accounts Payable and Other Liabilities [Member]	Jun. 30, 2012 Swap 1 [Member] Accounts Payable and Other Liabilities [Member]	Jun. 30, 2013 Swap 3 [Member] Accounts Payable and Other Liabilities [Member]	Jun. 30, 2012 Swap 3 [Member] Accounts Payable and Other Liabilities [Member]	Jun. 30, 2013 Swap 4 [Member] Accounts Payable and Other Liabilities [Member]	Jun. 30, 2012 Swap 4 [Member] Accounts Payable and Other Liabilities [Member]	Jun. 30, 2013 Swap 5 [Member] Accounts Payable and Other Liabilities [Member]	Jun. 30, 2012 Swap 5 [Member] Accounts Payable and Other Liabilities [Member]	Jun. 30, 2013 Swap 11 [Member] Accounts Payable and Other Liabilities [Member]	Jun. 30, 2012 Swap 11 [Member] Accounts Payable and Other Liabilities [Member]	Jun. 30, 2013 Swap 6 [Member] Accounts Payable and Other Liabilities [Member]	Jun. 30, 2012 Swap 6 [Member] Accounts Payable and Other Liabilities [Member]	Jun. 30, 2013 Swap 7 [Member] Accounts Payable and Other Liabilities [Member]	Jun. 30, 2012 Swap 7 [Member] Accounts Payable and Other Liabilities [Member]	Jun. 12, 2013 Swap 12 [Member] Accounts Payable and Other Liabilities [Member]	Jun. 30, 2013 Swap 12 [Member] Accounts Payable and Other Liabilities [Member]	Jun. 30, 2012 Swap 12 [Member] Accounts Payable and Other Liabilities [Member]	Jun. 30, 2013 Swap 8 [Member] Accounts Payable and Other Liabilities [Member]	Jun. 30, 2012 Swap 8 [Member] Accounts Payable and Other Liabilities [Member]	Jun. 30, 2013 Swap 9 [Member] Accounts Payable and Other Liabilities [Member]	Jun. 30, 2012 Swap 9 [Member] Accounts Payable and Other Liabilities [Member]	May 31, 2013 Swap 13 [Member] Accounts Payable and Other Liabilities [Member]	Jun. 30, 2013 Swap 13 [Member] Accounts Payable and Other Liabilities [Member]	Jun. 30, 2012 Swap 13 [Member] Accounts Payable and Other Liabilities [Member]	Jun. 30, 2013 Swap 10 [Member] Accounts Payable and Other Liabilities [Member]	Jun. 30, 2012 Swap 10 [Member] Accounts Payable and Other Liabilities [Member]	Jun. 30, 2013 Unsecured Term Loan $120 million [Member] Wells Fargo Bank [Member]	Jun. 12, 2013 Unsecured Term Loan $120 million [Member] Wells Fargo Bank [Member]	Jun. 30, 2013 Unsecured Term Loan $120 million [Member] Wells Fargo Bank [Member] Swap 12 [Member] Accounts Payable and Other Liabilities [Member]	Jun. 30, 2013 Unsecured Term Loan $125 million [Member] Key Bank [Member]	Mar. 25, 2013 Fund II Assets [Member] Swap	Jun. 30, 2013 Hayden Ferry Lakeside II [Member] sqft	Jun. 28, 2013 Hayden Ferry Lakeside II [Member] sqft	Mar. 25, 2013 Tampa Fund II Assets [Member] sqft	Jun. 28, 2013 Hayden Ferry II Modified Mortgage [Member] Hayden Ferry Lakeside II [Member]	Jun. 27, 2013 Hayden Ferry II Original Mortgage [Member] Hayden Ferry Lakeside II [Member]	Jun. 28, 2013 Hayden Ferry II Original Mortgage [Member] Hayden Ferry Lakeside II [Member]	Jun. 28, 2013 London Interbank Offered Rate (LIBOR) [Member] Hayden Ferry II Modified Mortgage [Member] Hayden Ferry Lakeside II [Member]	Aug. 03, 2013 Subsequent Event [Member] Hayden Ferry II Modified Mortgage [Member] Hayden Ferry Lakeside II [Member]	Aug. 01, 2013 Subsequent Event [Member] Hayden Ferry II Modified Mortgage [Member] Hayden Ferry Lakeside II [Member]
Derivative [Line Items]
Notional amount			$ 12,088,000		$ 50,000,000		$ 75,000,000		$ 33,875,000		$ 625,000		$ 22,000,000		$ 46,875,000		$ 120,000,000			$ 9,250,000		$ 22,500,000		$ 13,500,000			$ 22,100,000		$ 120,000,000			$ 125,000,000.0	$ 34,600,000.0
Maturity date			Nov. 18, 2015		Sep. 27, 2017		Sep. 27, 2017		Nov. 18, 2017		Jan. 25, 2018		Jan. 25, 2018		Jan. 25, 2018		Jun. 11, 2018			Sep. 30, 2018		Oct. 08, 2018		Oct. 08, 2018			Nov. 18, 2018											Jan. 01, 2018			Jan. 01, 2018
Reference rate (in hundredths)			1-month LIBOR		1-month LIBOR		1-month LIBOR		1-month LIBOR		1-month LIBOR		1-month LIBOR		1-month LIBOR			1-month LIBOR		1-month LIBOR		1-month LIBOR			1-month LIBOR		1-month LIBOR
Rate at which reference rate is fixed			4.10%		2.20%		2.20%		4.70%		4.94%		4.50%		4.71%					5.20%		5.40%					5.00%				3.10%
Fair market value liability	(7,046,000)	(14,356,000)	0	(642,000)	972,000	0	1,409,000	0	(2,171,000)	(3,359,000)	(29,000)	0	(1,178,000)	(1,912,000)	(411,000)	(1,344,000)		(1,216,000)	0	(793,000)	(1,241,000)	(2,077,000)	(3,204,000)		74,000	0	(1,626,000)	(2,654,000)
Remaining ownership by noncontrolling owners purchased (in percent)																																				70.00%
Number of interest rate swaps																																	2
Area of Real Estate Property																																		299,000	299,000	788,000
Frequency of principal payments on existing mortgage																																						quarterly
Quarterly principal payments on existing mortgages																																						625,000
Maturity date																																					Feb. 01, 2015
LIBOR																																								LIBOR
Fixed base rate of variable interest rate																																							1.50%			1.70%
Loan amount	$ 313,000,000																												$ 120,000,000	$ 120,000,000		$ 125,000,000