Real Estate and Accumulated Depreciation - Reconciliation of Real Estate and Accumulated Depreciation (Details) - USD ($)		12 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Balance-Beginning of Year		$ 941,009,905	$ 743,714,774	$ 627,866,051
Total Additions		230,303,590	202,851,508	115,848,723
Total Disposals		0	(5,556,377)	0
Balance-End of Year		1,171,313,495	941,009,905	743,714,774
Somerset, NJ [Member]
Total Additions		377,637	182,573	1,136,454
Monaca (Pittsburgh), PA [Member]
Total Additions		37,255	1,907,292	2,707,529
Orangeburg (New York), NY [Member]
Total Additions		0	96,800	108,157
Ridgeland (Jackson), MS [Member]
Total Additions		7,797	0	0
Urbandale (Des Moines), IA [Member]
Total Additions		0	0	0
Richland (Jackson), MS [Member]
Total Additions		0	0	422,691
O'Fallon (St. Louis), MO [Member]
Total Additions		0	317,457	20,744
Fayetteville, NC [Member]
Total Additions		557,354	13,773	0
Schaumburg (Chicago), IL [Member]
Total Additions		13,775	0	0
Burr Ridge (Chicago), IL [Member]
Total Additions		8,700	0	65,333
Romulus (Detroit), MI [Member]
Total Additions		0	116,919	0
Liberty (Kansas City), MO [Member]
Total Additions		24,263	2,500	26,620
Omaha, NE [Member]
Total Additions		7,410	7,391	0
Charlottesville, VA [Member]
Total Additions		4,462	0	0
Jacksonville, FL (FDX) [Member]
Total Additions		16,983	0	73,921
West Chester Twp (Cincinnati), OH [Member]
Total Additions		0	0	77,555
Richmond, VA (FDX) [Member]
Total Additions		18,510	7,356	14,152
St. Joseph, MO [Member]
Total Additions		50,934	53,922	11,980
Newington (Hartford), CT [Member]
Total Additions		0	0	18,000
Cudahy (Milwaukee), WI [Member]
Total Additions		8,689	0	0
Beltsville (Washington, DC), MD [Member]
Total Additions		44,600	9,271	71,700
Granite City (St. Louis, MO), IL [Member]
Total Additions		156,139	0	0
Monroe, NC [Member]
Total Additions		0	55,680	10,875
Winston Salem, NC [Member]
Total Additions		316,527	0	8,101
Elgin (Chicago), IL [Member]
Total Additions		5,960	30,312	29,048
Tolleson (Phoenix), AZ [Member]
Total Additions		1,655,640	(3,925)	13,015
Ft. Myers, FL [Member]
Total Additions		0	0	13,321
Edwardsville (Kansas City), KS (Carlisle) [Member]
Total Additions		0	0	200,000
Tampa, FL (FDX Ground) [Member]
Total Additions	[1]	1,247,140	6,147	688,990
Denver, CO [Member]
Total Additions		0	0	0
Hanahan (Charleston), SC (SAIC) [Member]
Total Additions		40,000	328,118	0
Hanahan (Charleston), SC (FDX Ground) [Member]
Total Additions		0	0	7,983
Augusta, GA (FDX Ground) [Member]
Total Additions		25,161	0	0
Huntsville, AL [Member]
Total Additions	[2]	1,853,390	0	0
Richfield (Cleveland), OH [Member]
Total Additions		0	(91,709)	4,655,309
Colorado Springs, CO [Member]
Total Additions		9,357	0	0
Tampa, FL (FDX) [Member]
Total Additions		27,144	0	0
Griffin (Atlanta), GA [Member]
Total Additions		0	0	0
Roanoke, VA (CHEP) [Member]
Total Additions		0	(59,348)	649,101
Orion, MI [Member]
Total Additions		5,867	5,021	61,507
Carlstadt, NJ (New York, NY) [Member]
Total Additions		13,877	51,120	0
Wheeling (Chicago), IL [Member]
Total Additions		0	0	0
White Bear Lake (Minneapolis/St. Paul), MN [Member]
Total Additions		0	0	0
Cheektowaga (Buffalo), NY [Member]
Total Additions		0	0	28,766
Richmond, VA (Carrier) [Member]
Total Additions		7,540	19,764	29,964
Montgomery (Chicago), IL [Member]
Total Additions		0	0	0
Tampa, FL (Tampa Bay Grand Prix) [Member]
Total Additions		26,916	0	34,192
Augusta, GA (FDX) [Member]
Total Additions		24,700	6,850	13,250
Lakeland, FL [Member]
Total Additions		16,321	0	6,643
El Paso, TX [Member]
Total Additions		0	1,198,544	323,326
Chattanooga, TN [Member]
Total Additions		41,042	0	0
Bedford Heights (Cleveland), OH [Member]
Total Additions		84,288	4,450	58,309
Kansas City, MO (Kellogg) [Member]
Total Additions		52,100	0	0
Punta Gorda, FL [Member]
Total Additions		8,350	0	0
Cocoa, FL [Member]
Total Additions		37,606	73,962	3,494,426
Orlando, FL [Member]
Total Additions		13,195	0	4,833
Topeka, KS [Member]
Total Additions		0	0	0
Memphis, TN [Member]
Total Additions		0	0	20,887
Houston, TX [Member]
Total Additions		0	2,279	0
Carrollton (Dallas), TX [Member]
Total Additions		24,806	4,300	0
Ft. Mill (Charlotte, NC), SC [Member]
Total Additions		0	0	338,833
Lebanon (Nashville), TN [Member]
Total Additions		0	0	0
Rockford, IL (Sherwin-Williams) [Member]
Total Additions		0	11,227	0
Edinburg, TX [Member]
Total Additions	[3]	3,985,389	0	24,483
Streetsboro (Cleveland), OH [Member]
Total Additions		0	0	0
Corpus Christi, TX [Member]
Total Additions		0	0	0
Halfmoon (Albany), NY [Member]
Total Additions		0	0	0
Lebanon (Cincinnati), OH [Member]
Total Additions		0	36,425	0
Olive Branch, MS (Memphis, TN) (Anda) [Member]
Total Additions		0	0	0
Oklahoma City, OK [Member]
Total Additions	[4]	(13,611)	2,989,708	0
Waco, TX [Member]
Total Additions		0	3,813,157	0
Livonia (Detroit), MI [Member]
Total Additions		31,497	30,533	0
Olive Branch, MS (Memphis, TN)(Milwaukee Tool) [Member]
Total Additions	[5]	9,412,120	133,981	0
Roanoke, VA (FDX Ground) [Member]
Total Additions		0	0	0
Green Bay, WI [Member]
Total Additions		0	0	0
Stewartville (Rochester), MN [Member]
Total Additions		0	0	0
Tulsa, OK [Member]
Total Additions		0	48,031	3,700,000
Buckner (Louisville), KY [Member]
Total Additions		48,136	86,591	26,633,125
Edwardsville (Kansas City), KS (International Paper) [Member]
Total Additions		5,355	203,261	18,085,492
Altoona, PA [Member]
Total Additions		18,650	0	8,990,000
Spring (Houston), TX [Member]
Total Additions		56,275	1,415	19,226,108
Indianapolis, IN (FDX Ground) [Member]
Total Additions		0	202,000	23,744,000
Sauget (St. Louis, MO), IL [Member]
Total Additions		4,950	15,200,000	0
Lindale (Tyler), TX [Member]
Total Additions		0	9,930,000	0
Kansas City, MO (Bunzl) [Member]
Total Additions		0	9,600,000	0
Frankfort (Lexington), KY [Member]
Total Additions		0	28,000,000	0
Jacksonville, FL (FDX Ground) [Member]
Total Additions		0	30,645,954	0
Monroe (Cincinnati), OH [Member]
Total Additions		0	12,937,000	0
Greenwood (Indianapolis), IN [Member]
Total Additions		15,817	37,484,574	0
Ft. Worth (Dallas), TX [Member]
Total Additions		0	35,300,832	0
Cincinnati, OH [Member]
Total Additions		0	6,750,000	0
Rockford, IL (B/E Aerospace) [Member]
Total Additions		0	5,100,000	0
Concord (Charlotte), NC [Member]
Total Additions		31,975,897	0	0
Covington (New Orleans), LA [Member]
Total Additions		18,410,000	0	0
Imperial (Pittsburgh), PA [Member]
Total Additions		19,950,000	0	0
Burlington (Seattle/Everett), WA [Member]
Total Additions		30,210,680	0	0
Colorado Springs, CO [Member]
Total Additions		28,500,000	0	0
Louisville, KY [Member]
Total Additions		11,304,000	0	0
Davenport (Orlando), FL [Member]
Total Additions		37,780,000	0	0
Olathe (Kansas City), KS [Member]
Total Additions		$ 31,737,000	$ 0	$ 0

[1] Parking lot expansion completed in August 2016

[2] 14,941 square foot building expansion was completed in August 2016.

[3] 50,741 square foot building expansion was completed in October 2016

[4] Reversal of over accrual from prior year contract payable on expansion completed in fiscal year 2015

[5] 246,434 square foot building expansion was completed in July 2016