Shareholders' Equity - Trust (Common Shares) (Details)	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2017 USD ($) shares	Sep. 30, 2017 USD ($) shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Aug. 31, 2015 USD ($)
Common Units
Units issued in connection with acquisitions | shares			0	0	0
Continuous Equity Offering
Maximum equity capacity | $	$ 200,000,000		$ 200,000,000
Equity available | $	$ 125,000,000		$ 125,000,000
Shares issued during period under continuous equity offerings, shares, new issues | shares			0	0	0
Share Repurchase
Share repurchase, value | $				$ 40,896,000	$ 71,802,000
Common units [Member]
Common Shares
Common units distributions (USD per share) | $			$ 252,300,000	$ 285,900,000	$ 289,300,000
Ordinary dividend (USD per share) | $ / shares			$ 1.5369	$ 1.0319	$ 1.4348
Qualified dividend (USD per share) | $ / shares			0.0150	0.0013	0
Capital gain - 20% (USD per share) | $ / shares			0.0482	0	0.1112
IRC Sec 1250 unrecapture gain - 25% (USD per share) | $ / shares			0.0749	0.6176	0.3372
Return of capital (USD per share) | $ / shares			0	0.2492	0.0168
Total (USD per share) | $ / shares			$ 1.675	$ 1.90	$ 1.90
Common shares [Member]
Dividend Reinvestment and Share Purchase Plan
Dividend reinvestment plan | shares			42,366	56,426	1,036,437
Share Repurchase
Share repurchase, shares | shares				1,396,844	2,321,794
2015 Share Repurchase Program [Member] | Common shares [Member]
Share Repurchase
Stock repurchase program, authorized amount | $						$ 250,000,000
Share repurchase, shares | shares			0	1,400,000	2,300,000
Share repurchase, value | $				$ 40,900,000	$ 71,800,000
2017 Share Repurchase Program [Member] | Common shares [Member]
Share Repurchase
Stock repurchase program, authorized amount | $		$ 250,000,000
Share repurchase, shares | shares	0
Liberty Property Limited Partnership [Member]
Common Units
Common units outstanding | shares	3,520,205		3,520,205	3,530,031
Closing price of the common shares | $	$ 151,400,000		$ 151,400,000
Units issued in connection with acquisitions | shares			0	0	0
Share Repurchase
Share repurchase, value | $				$ 40,896,000	$ 71,802,000
Liberty Property Limited Partnership [Member] | Common units [Member]
Dividend Reinvestment and Share Purchase Plan
Dividend reinvestment plan | shares			42,366	56,426	1,036,437
Liberty Property Limited Partnership [Member] | 2015 Share Repurchase Program [Member] | Common units [Member]
Share Repurchase
Stock repurchase program, authorized amount | $		$ 250,000,000				$ 250,000,000
Share repurchase, shares | shares		0		1,400,000	2,300,000
Share repurchase, value | $				$ 40,900,000	$ 71,800,000
Liberty Property Limited Partnership [Member] | 2017 Share Repurchase Program [Member] | Common units [Member]
Share Repurchase
Share repurchase, shares | shares	0
Conversion Ratio of Common Units to Common Shares [Member]
Common Units
Common unit, convertible to common stock	1		1
Common stock, converted from common unit	1		1