SCHEDULE III - REAL ESTATE PROPERTIES AND ACCUMULATED DEPRECIATION - Notes to Schedule (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2018	Sep. 30, 2014
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation Disclosure [Abstract]
Total real estate properties				$ 1,147,911
Less: Accumulated depreciation and amortization				(88,109)
Net real estate properties	$ 1,059,802	$ 911,250	$ 793,572	$ 1,059,802	$ 757,027
Reconciliation of real estate properties
Balance at beginning of year	911,250	793,572
Additions:
Acquisitions	233,400	239,923	318,680
Capital improvements	24,443	9,298	19,649
Capitalized development expenses and carrying costs	33,609	16,069	27,194
Total additions	291,452	265,290	365,523
Deductions:
Sales	103,654	113,552	150,786
Depreciation / amortization / paydowns	38,504	30,489	24,328
Other dispositions	742	3,571	0
Reconciliation of partnership interest	0	0	153,864
Total deductions	142,900	147,612	328,978
Balance at end of year	$ 1,059,802	$ 911,250	$ 793,572