Fair Value (Schedule Of Financial Assets And Liabilities At Fair Value) (Details) - USD ($)	Jun. 30, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments in U.S. Treasury notes held in equity trading accounts as collateral	$ 35,416,755	$ 26,059,657	$ 36,536,889
Investments in U.S. Treasury notes held in custody	165,659,765	175,334,307	148,800,124
Total investments in U.S. Treasury notes	201,076,520	201,393,964	185,337,013
Short-term money market fund	17,067,053	18,621,676	11,490,322
Net unrealized appreciation on open futures and forward currency contracts		5,065,066	4,388,065
Net unrealized depreciation on open futures and forward currency contracts	(11,468,723)		(128,211)
Total futures and forward currency contracts	(11,468,723)	5,065,066	4,259,854
Total financial assets at fair value		225,080,706	201,087,189
Futures Contracts [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total futures and forward currency contracts	(10,070,923)	3,403,431	2,662,171
Energies [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total futures and forward currency contracts	(1,321,328)	(30,169)	1,506,235
Grains [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total futures and forward currency contracts	(707,267)	28,884	336,843
Interest Rates [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total futures and forward currency contracts	(5,574,794)	2,204,441	(299,778)
Livestock [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total futures and forward currency contracts	(38,220)	(790)	(88,790)
Metals [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total futures and forward currency contracts	(145,179)	347,170	570,378
Softs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total futures and forward currency contracts	173,328	(16,816)	(32,325)
Stock Indices [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total futures and forward currency contracts	(2,457,463)	870,711	669,608
Forward Currency Contracts [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total futures and forward currency contracts	(1,397,800)	1,661,635	1,597,683
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments in U.S. Treasury notes	201,076,520	201,393,964	185,337,013
Short-term money market fund	17,067,053	18,621,676	11,490,322
Total futures and forward currency contracts		3,403,431	2,662,171
Total financial assets at fair value		223,419,071	199,489,506
Level 1 [Member] | Futures Contracts [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total futures and forward currency contracts	(10,070,923)	3,403,431	2,662,171
Level 1 [Member] | Energies [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total futures and forward currency contracts	(1,321,328)	(30,169)	1,506,235
Level 1 [Member] | Grains [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total futures and forward currency contracts	(707,267)	28,884	336,843
Level 1 [Member] | Interest Rates [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total futures and forward currency contracts	(5,574,794)	2,204,441	(299,778)
Level 1 [Member] | Livestock [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total futures and forward currency contracts	(38,220)	(790)	(88,790)
Level 1 [Member] | Metals [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total futures and forward currency contracts	(145,179)	347,170	570,378
Level 1 [Member] | Softs [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total futures and forward currency contracts	173,328	(16,816)	(32,325)
Level 1 [Member] | Stock Indices [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total futures and forward currency contracts	(2,457,463)	870,711	669,608
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total futures and forward currency contracts		1,661,635	1,597,683
Total financial assets at fair value		1,661,635	1,597,683
Level 2 [Member] | Forward Currency Contracts [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total futures and forward currency contracts	$ (1,397,800)	$ 1,661,635	$ 1,597,683