Debt - Textuals (Details) (USD $)			12 Months Ended	0 Months Ended				0 Months Ended		12 Months Ended	0 Months Ended			12 Months Ended	0 Months Ended						12 Months Ended		0 Months Ended				12 Months Ended		12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013 Mortgages	Mar. 28, 2013 Secured Real Estate Term Loan	Dec. 31, 2013 Secured Real Estate Term Loan	Dec. 31, 2012 Secured Real Estate Term Loan	Mar. 28, 2013 Secured Real Estate Term Loan Interest Rate Swap	Mar. 07, 2013 Unsecured Revolving Credit Facility JPMorgan Securities, LLC, Wells Fargo Securities, LLC and Deutsche Bank Securities Inc.	Mar. 29, 2012 Unsecured Revolving Credit Facility JPMorgan Securities, LLC, Wells Fargo Securities, LLC and Deutsche Bank Securities Inc.	Dec. 31, 2013 Unsecured Revolving Credit Facility JPMorgan Securities, LLC, Wells Fargo Securities, LLC and Deutsche Bank Securities Inc.	Mar. 07, 2013 Unsecured Revolving Credit Facility JPMorgan Securities, LLC, Wells Fargo Securities, LLC and Deutsche Bank Securities Inc. Minimum	Mar. 07, 2013 Unsecured Revolving Credit Facility JPMorgan Securities, LLC, Wells Fargo Securities, LLC and Deutsche Bank Securities Inc. Maximum	Mar. 29, 2012 Unsecured Term Loans JPMorgan Securities, LLC, Wells Fargo Securities, LLC and Deutsche Bank Securities Inc.	Dec. 31, 2013 Unsecured Term Loans JPMorgan Securities, LLC, Wells Fargo Securities, LLC and Deutsche Bank Securities Inc.	Jan. 07, 2014 Unsecured Term Loans JPMorgan Securities, LLC, Wells Fargo Securities, LLC and Deutsche Bank Securities Inc. Subsequent Event	Mar. 29, 2012 Unsecured Term Loans JPMorgan Securities, LLC, Wells Fargo Securities, LLC and Deutsche Bank Securities Inc. Minimum	Jan. 07, 2014 Unsecured Term Loans JPMorgan Securities, LLC, Wells Fargo Securities, LLC and Deutsche Bank Securities Inc. Minimum Subsequent Event	Mar. 29, 2012 Unsecured Term Loans JPMorgan Securities, LLC, Wells Fargo Securities, LLC and Deutsche Bank Securities Inc. Maximum	Jan. 07, 2014 Unsecured Term Loans JPMorgan Securities, LLC, Wells Fargo Securities, LLC and Deutsche Bank Securities Inc. Maximum Subsequent Event	Dec. 31, 2013 Unsecured Term Loans JPMorgan Securities, LLC, Wells Fargo Securities, LLC and Deutsche Bank Securities Inc., With Interest Rate Swap	Dec. 31, 2013 Unsecured Term Loans Wells Fargo	Jul. 20, 2012 Unsecured Term Loans Wells Fargo	Jul. 20, 2012 Unsecured Term Loans Wells Fargo Minimum	Jul. 20, 2012 Unsecured Term Loans Wells Fargo Maximum	Dec. 31, 2013 Unsecured Term Loans Wells Fargo, With Interest Rate Swap	Mar. 28, 2013 Unsecured Senior Notes	Dec. 31, 2013 Variable Rate Mortgages Mortgages loan	Dec. 31, 2012 Variable Rate Mortgages Mortgages	Dec. 31, 2013 Fixed Rate Mortgages Mortgages loan	Dec. 31, 2012 Fixed Rate Mortgages Mortgages
Debt Instrument
Line of credit facility, borrowing capacity								$ 650,000,000.0	$ 575,000,000
Long-term debt	1,213,676,000	1,034,956,000			0	125,500,000							300,000,000									155,000,000				300,000,000	29,925,000	0	373,751,000	382,456,000
Line of credit facility, maximum borrowing capacity, increase in capacity								75,000,000.0
Unsecured credit agreement, extension option period									1 year				1 year
Description of variable rate basis								LIBOR					LIBOR
Basis spread on variable rate										1.30%	1.10%	1.75%		1.55%	1.20%	1.30%	1.05%	2.25%	1.95%		1.70%		1.55%	2.40%
Line of credit facility, unused capacity, commitment fee percentage										0.25%	0.20%	0.50%
Debt instrument, effective interest rate																				2.60%					2.99%	3.80%
Debt instrument, stated interest rate																										3.70%
Debt instrument, percentage of principal amount received																										99.186%
Effective percentage rate range, minimum			1.62%
Effective percentage rate range, maximum			12.75%
Weighted average interest rate			5.56%
Weighted average interest rate with interest rate swap impact																											5.80%
Number of mortgage loans assumed																											1		3
Repayments of debt				125,500,000
Notional amount terminated							$ 75,000,000