Non-Controlling Interests, Preferred Shares, Common Shares and Common Shares in Treasury - Preferred Shares Outstanding (Parenthetical) (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Class J Cumulative Redeemable Preferred Shares [Member]
Preferred Shares Outstanding [Line Items]
Preferred equity fixed dividend rate per annum	6.50%	6.50%
Cumulative redeemable preferred shares liquidation value	$ 500	$ 500
Cumulative redeemable preferred shares authorized	750,000	750,000
Cumulative redeemable preferred shares issued	400,000	400,000
Cumulative redeemable preferred shares outstanding	400,000	400,000
Class K Cumulative Redeemable Preferred Shares [Member]
Preferred Shares Outstanding [Line Items]
Preferred equity fixed dividend rate per annum	6.25%	6.25%
Cumulative redeemable preferred shares liquidation value	$ 500	$ 500
Cumulative redeemable preferred shares authorized	750,000	750,000
Cumulative redeemable preferred shares issued	300,000	300,000
Cumulative redeemable preferred shares outstanding	300,000	300,000