Capital and Financing Transactions, Interest Rate Swaps (Details) (USD $) In Thousands, unless otherwise specified					6 Months Ended			6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 Minimum [Member]	Jun. 30, 2012 Maximum [Member]	Jun. 30, 2012 Hayden Ferry Lakeside II [Member]	Feb. 10, 2012 Hayden Ferry Lakeside II [Member]	May 31, 2012 Pinnacle and Parking at Jackson Place [Member]	Jun. 30, 2012 Swap 1 [Member]	Jun. 30, 2011 Swap 1 [Member]	Jun. 30, 2012 Swap 2 [Member]	Jun. 30, 2011 Swap 2 [Member]	Jun. 30, 2012 Swap 3 [Member]	Jun. 30, 2011 Swap 3 [Member]	Jun. 30, 2012 Swap 4 [Member]	Jun. 30, 2011 Swap 4 [Member]	Jun. 30, 2012 Swap 5 [Member]	Jun. 30, 2011 Swap 5 [Member]	Jun. 30, 2012 Swap 6 [Member]	Jun. 30, 2011 Swap 6 [Member]	Jun. 30, 2012 Swap 7 [Member]	Jun. 30, 2011 Swap 7 [Member]	Jun. 30, 2012 Swap 8 [Member]	Jun. 30, 2011 Swap 8 [Member]
Derivative [Line Items]
Notional amount						$ 50,000	$ 23,500	$ 23,500		$ 12,088		$ 33,875		$ 22,000		$ 49,375		$ 9,250		$ 22,500		$ 22,100
Reference rate (in hundredths)					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 (in hundredths)					1.50%
Maturity date					Jan. 25, 2018			Dec. 01, 2014		Nov. 18, 2012		Nov. 18, 2017		Jan. 25, 2018		Jan. 25, 2018		Sep. 30, 2018		Oct. 08, 2018		Nov. 18, 2018
Basis spread on variable rate (in hundredths)			25000.00%	35000.00%
Variable rate, minimum (in hundredths)						4.00%
Variable rate, maximum (in hundredths)						5.00%
Fixed rate (in hundredths)							5.80%	5.80%		4.10%		4.70%		4.50%		5.00%		5.20%		5.40%		5.00%
Fair market value liability	$ (14,356)	$ (5,438)						$ 0	$ (2,222)	$ (642)	$ (225)	$ (3,359)	$ (797)	$ (1,912)	$ 0	$ (1,344)	$ 0	$ (1,241)	$ (420)	$ (3,204)	$ (1,209)	$ (2,654)	$ (565)