Non-Controlling Interests, Preferred Shares, Common Shares and Common Shares in Treasury - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Schedule Of Equity [Line Items]
Operating partnership units outstanding	369,176	369,176
Common shares, par value	$ 0.10	$ 0.10
Class A Cumulative Redeemable Preferred Shares [Member]
Schedule Of Equity [Line Items]
Cumulative redeemable preferred shares	$ 175,000	$ 0
Preferred stock dividend rate	6.375%
Cumulative redeemable preferred shares, liquidation value	$ 500
Preferred Shares, without par value	750,000
Class A Depositary Share [Member]
Schedule Of Equity [Line Items]
Cumulative redeemable preferred shares, liquidation value	$ 25
Redemption date restrictions for depositary shares	Jun. 05, 2022
Class K Depositary Share [Member]
Schedule Of Equity [Line Items]
Cumulative redeemable preferred shares, liquidation value	$ 500
Redemption date restrictions for depositary shares	Apr. 09, 2018
Class J Depositary Share [Member]
Schedule Of Equity [Line Items]
Cumulative redeemable preferred shares, liquidation value	$ 500
Class A Cumulative Redeemable Preferred Shares [Member]
Schedule Of Equity [Line Items]
Preferred Shares, without par value	750,000
Class B Cumulative Redeemable Preferred Shares [Member]
Schedule Of Equity [Line Items]
Preferred Shares, without par value	750,000
Class C Cumulative Redeemable Preferred Shares [Member]
Schedule Of Equity [Line Items]
Preferred Shares, without par value	750,000
Class D Cumulative Redeemable Preferred Shares [Member]
Schedule Of Equity [Line Items]
Preferred Shares, without par value	750,000
Class E Cumulative Redeemable Preferred Shares [Member]
Schedule Of Equity [Line Items]
Preferred Shares, without par value	750,000
Class F Cumulative Redeemable Preferred Shares [Member]
Schedule Of Equity [Line Items]
Preferred Shares, without par value	750,000
Class G Cumulative Redeemable Preferred Shares [Member]
Schedule Of Equity [Line Items]
Preferred Shares, without par value	750,000
Class H Cumulative Redeemable Preferred Shares [Member]
Schedule Of Equity [Line Items]
Preferred Shares, without par value	750,000
Class I Cumulative Redeemable Preferred Shares [Member]
Schedule Of Equity [Line Items]
Preferred Shares, without par value	750,000
Class J Cumulative Redeemable Preferred Shares [Member]
Schedule Of Equity [Line Items]
Preferred Shares, without par value	750,000
Class K Cumulative Redeemable Preferred Shares [Member]
Schedule Of Equity [Line Items]
Preferred Shares, without par value	750,000
Non-Cumulative Preferred Shares [Member]
Schedule Of Equity [Line Items]
Preferred Shares, without par value	750,000
Cumulative Voting Preferred Shares [Member]
Schedule Of Equity [Line Items]
Preferred Shares, without par value	2,000,000