Selected Quarterly Financial Information (unaudited) (Details) - USD ($)	3 Months Ended	12 Months Ended
Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Selected Quarterly Financial Information (unaudited)
Revenues	$ 39,034,678	$ 44,545,589	$ 34,729,021	$ 41,025,472	$ 47,585,174	$ 35,734,988	$ 33,611,233	$ 50,515,776	$ 159,334,760	$ 167,447,171	$ 289,207,829
Operating income/(loss)	673,447	6,996,104	(3,534,720)	(293,446)	9,244,855	(3,453,959)	(4,210,840)	12,413,266	3,841,385	13,993,322	158,415,187
Net income/(loss)	$ (3,465,995)	$ 1,670,415	$ (11,915,136)	$ (6,689,970)	$ 1,955,240	$ 5,039,624	$ (7,145,558)	$ (1,291,121)	$ (20,400,686)	$ (1,441,815)	$ 129,688,382
Earnings/(loss) per common share—basic and diluted (in dollars per share)	$ (0.06)	$ 0.03	$ (0.22)	$ (0.12)	$ 0.04	$ 0.09	$ (0.13)	$ (0.02)

The amount of net income or loss for the period per each share in instances when basic and diluted earnings per share are the same amount and reported as a single line item on the face of the financial statements. Basic earnings per share is the amount of net income or loss for the period per each share of common stock or unit outstanding during the reporting period. Diluted earnings per share includes the amount of net income or loss for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

No definition available.

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- Definition

Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=96947427&loc=d3e1377-109256

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- Definition

The net result for the period of deducting operating expenses from operating revenues.

+ References

No definition available.

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- References

No definition available.

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- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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