4. Debt Unsecured Term Loan (Details) (USD $)			9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013 Unsecured Term Loan [Member]	Sep. 30, 2013 Maximum [Member] Unsecured Term Loan [Member]	Sep. 30, 2013 Minimum [Member] Unsecured Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Issuance Date			Sep. 13, 2013
Unsecured Term Loan	$ 120,000,000	$ 0	$ 195,000,000
Debt Instrument, Maturity Date			Feb. 15, 2019
Unsecured Term Loan Initial Advance			120,000,000
Unsecured Term Loan Remaining Balance To Be Drawn			75,000,000
Unsecured Term Loan Draw Minimum Increment			25,000,000
Delayed Draw Deadline			Jan. 10, 2014
Unsecured Term Loan Accordion Increase Amount			55,000,000
Accordion Exercise Date			Oct. 18, 2013
Unsecured Term Loan with Accordion			250,000,000
Unsecured Term Loan Accordion Closing Advance			34,000,000
Unsecured Term Loan Remaining Balance To Be Drawn Including Accordion			96,000,000
Unsecured Debt To Unencumbered Assets				60.00%
Income from Unencumbered Assets To Unsecured Debt					12.50%
Ratio of Total Indebtedness To Gross Assets Value				60.00%
Fixed Charge Coverage Ratio					1.70
Tangible Net Worth Amount					$ 1,300,000,000
Percentage Of Equity Offerings And Interests In Operating Partnerships To Be Added To Tangible Net Worth Threshold					80.00%