Equity - Additional Information (Details) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended	9 Months Ended
	Jul. 31, 2015 USD ($) shares	Jul. 31, 2014 USD ($)	Sep. 30, 2015 USD ($) $ / shares shares	Sep. 30, 2015 USD ($) $ / shares shares	Sep. 30, 2014 USD ($) shares	Dec. 31, 2014 USD ($)
Equity [Line Items]
Proceeds from issuance of common shares | $				$ 17,312	$ 19,165
Authorized amount (in shares)	10,000,000
Treasury stock acquired (in shares)			1,306,300
Treasury stock acquired, average cost (in dollars per share) | $ / shares			$ 8.42
Gains and losses on cash flow hedges | $			$ (6,216)	$ (6,216)		$ 404
OP unit equivalent in common shares				1.13
Cash and stock issued during period, value, conversion of units | $					$ 1,962
Partners capital account, shares issued for units redeemed					11,186
Partners' capital account, units			3,422,000	3,422,000
Payments to acquire interest in joint venture | $				$ 4,022	$ 2,100
Parent [Member]
Equity [Line Items]
Partners' capital account, redemption for common shares | $					$ 56
Former LCIF II Partners [Member]
Equity [Line Items]
Partners capital account, units exchanged for cash					170,193
Cash and stock issued during period, value, conversion of units | $					$ 1,962
Philadelphia Pennsylvania [Member] | Office Building [Member]
Equity [Line Items]
Payments to acquire interest in joint venture | $	$ 4,022	$ 2,100
Real estate, ownership percentage	100.00%
Direct Share Purchase Plan [Member]
Equity [Line Items]
Common shares issued during period				1,845,617	1,853,988
Proceeds from issuance of common shares | $				$ 17,415	$ 18,758
Trustees [Member]
Equity [Line Items]
Deferred compensation arrangement with individual, shares issued				20,400	14,000
Deferred compensation arrangement with individual, fair value of shares issued | $				$ 209	$ 142
Performance Shares [Member]
Equity [Line Items]
Grants in period				170,650
Weighted average grant date fair value | $				$ 1,916
Award vesting period				3 years
Performance Shares [Member] | Executive Officer [Member]
Equity [Line Items]
Measurement period				3 years
Index Performance Shares [Member] | Executive Officer [Member]
Equity [Line Items]
Measurement period basis				321,018
Fair value per share (in dollars per share) | $ / shares			$ 6.86	$ 6.86
Peer Performance Shares [Member] | Executive Officer [Member]
Equity [Line Items]
Measurement period basis				321,011
Fair value per share (in dollars per share) | $ / shares			$ 6.66	$ 6.66