CONSOLIDATED STATEMENTS OF EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Preferred Shares	Common Stock	Accumulated Distributions In Excess of Net Income	Accumulated Other Comprehensive Income	Noncontrolling Interest	Series A Preferred Stock	Series A Preferred Stock Accumulated Distributions In Excess of Net Income	Series B Preferred Stock	Series B Preferred Stock Accumulated Distributions In Excess of Net Income	Series C Preferred Stock	Series C Preferred Stock Preferred Shares	Series C Preferred Stock Accumulated Distributions In Excess of Net Income
Balance at Apr. 30, 2015	$ 740,954	$ 138,674	$ 951,868	$ (438,432)	$ 0	$ 88,844
Balance (in shares) at Apr. 30, 2015			12,446
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) attributable to controlling interest and noncontrolling interests	76,568			72,006		4,562
Distributions – common shares and Units	(71,290)			(64,060)		(7,230)
Distributions - preferred shares	(11,514)						$ (2,372)	$ (2,372)	$ (9,142)	$ (9,142)
Distribution reinvestment and share purchase plan (in shares)			82
Distribution reinvestment and share purchase plan	5,619		$ 5,619
Shares issued and share-based compensation (in shares)			19
Shares issued and share-based compensation	1,728		$ 1,728
Partnership units issued	18,226					18,226
Redemption of units for common shares (in shares)			27
Redemption of Units for common shares	0		$ 1,477			(1,477)
Shares repurchased (in shares)			(464)
Shares repurchased	(35,000)		$ (35,000)
Distributions to nonredeemable noncontrolling interests – consolidated real estate entities	(7,029)					(7,029)
Adjustments to prior year redemption of Units for common shares	0		(3,608)			3,608
Balance at Apr. 30, 2016	718,262	138,674	$ 922,084	(442,000)	0	99,504
Balance (in shares) at Apr. 30, 2016			12,110
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) attributable to controlling interest and noncontrolling interests	30,947			43,347		(12,400)
Distributions – common shares and Units	(63,360)			(55,907)		(7,453)
Distributions - preferred shares	(10,546)						$ (1,403)	$ (1,403)	(9,143)	(9,143)
Shares issued and share-based compensation (in shares)			39
Shares issued and share-based compensation	358		$ 358
Redemption of units for common shares (in shares)			50
Redemption of Units for common shares	0		$ 875			(875)
Redemption of units for cash	(966)					(966)
Shares repurchased (in shares)			(79)
Shares repurchased	(33,253)	(27,317)	$ (4,501)	(1,435)
Contributions from nonredeemable noncontrolling interests – consolidated real estate entities	7,188					7,188
Conversion to equity of notes receivable from nonredeemable noncontrolling interests – consolidated real estate entities	(7,366)					(7,366)
Acquisition of nonredeemable noncontrolling interests – consolidated real estate entities	(4,874)		$ (9,893)			5,019
Other (in shares)			0
Other	(232)		$ (18)			(214)
Balance at Apr. 30, 2017	636,158	111,357	$ 908,905	(466,541)	0	82,437
Balance (in shares) at Apr. 30, 2017			12,120
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) attributable to controlling interest and noncontrolling interests	128,370			116,788		11,582
Other comprehensive income - derivative instrument	1,779				1,779
Distributions – common shares and Units	(37,785)			(33,689)		(4,096)
Distributions - preferred shares	(8,569)								$ (4,571)	$ (4,571)	$ (3,999)		$ (3,999)
Shares issued and share-based compensation (in shares)			10
Shares issued and share-based compensation	1,663		$ 1,663
Issuance of Series C preferred shares											99,456	$ 99,456
Redemption of units for common shares (in shares)			3
Redemption of Units for common shares	0		$ 34			(34)
Redemption of units for cash	(8,775)					(8,775)
Shares repurchased (in shares)			(178)
Shares repurchased	(124,949)	(111,357)	$ (9,935)	(3,657)
Contributions from nonredeemable noncontrolling interests – consolidated real estate entities	619					619
Conversion to equity of notes receivable from nonredeemable noncontrolling interests – consolidated real estate entities	(246)					(246)
Other (in shares)			(2)
Other	(157)		$ (570)			413
Balance at Apr. 30, 2018	687,563	99,456	$ 900,097	(395,669)	1,779	81,900
Balance (in shares) at Apr. 30, 2018			11,953
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss) attributable to controlling interest and noncontrolling interests	(4,878)			(4,398)		(480)
Other comprehensive income - derivative instrument	(2,635)				(2,635)
Distributions – common shares and Units	(27,977)			(25,060)		(2,917)
Distributions - preferred shares	(4,547)										$ (4,548)		$ (4,548)
Shares issued and share-based compensation (in shares)			3
Shares issued and share-based compensation	1,042		$ 1,042
Redemption of units for common shares (in shares)			33
Redemption of Units for common shares	0		$ 649			(649)
Redemption of units for cash	(498)					(498)
Shares repurchased (in shares)			(42)
Shares repurchased	(2,172)		$ (2,172)
Distributions to nonredeemable noncontrolling interests – consolidated real estate entities	(2,432)					(2,432)
Conversion to equity of notes receivable from nonredeemable noncontrolling interests – consolidated real estate entities	(392)					(392)
Acquisition of nonredeemable noncontrolling interests – consolidated real estate entities	(44)		$ (175)			131
Other (in shares)			(5)
Other	(207)		$ (207)
Balance at Dec. 31, 2018	$ 643,449	$ 99,456	$ 899,234	$ (429,048)	$ (856)	$ 74,663
Balance (in shares) at Dec. 31, 2018			11,942