Debt - Net (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Debt Instrument
Total debt, gross	$ 1,213,676,000	$ 1,034,956,000
Net premium (discount)	565,000	2,403,000
Total	1,214,241,000	1,037,359,000
Unsecured Term Loans
Debt Instrument
Total debt, gross	455,000,000	455,000,000
Unsecured Senior Notes
Debt Instrument
Total debt, gross	300,000,000	0
Secured Real Estate Term Loan
Debt Instrument
Total debt, gross	0	125,500,000
Unsecured Revolving Credit Facility
Debt Instrument
Line of credit facility, amount outstanding	55,000,000	72,000,000
Fixed Rate Mortgages | Mortgages
Debt Instrument
Total debt, gross	373,751,000	382,456,000
Variable Rate Mortgages | Mortgages
Debt Instrument
Total debt, gross	$ 29,925,000	$ 0