Impact on Previously Issued Financial Statements for the Correction of an Error, Revised Consolidated Statement of Cash Flow from Operating Activities (Details) - USD ($)	3 Months Ended					6 Months Ended		9 Months Ended	12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Consolidated Statement of Cash Flow from Operating Activities [Abstract]
Net income (loss)	$ 3,513,000			$ 5,595,000	$ 7,820,000	$ (1,982,000)	$ 13,415,000
Deferred income taxes					209,000	(667,000)	(207,000)
Income tax receivable						(3,595,000)	(3,985,000)
Prepaid expenses and other current assets						(658,000)	(2,645,000)
Other assets					(1,000)	(79,000)	(20,000)
Accounts payable and accrued liabilities						17,840,000	(3,764,000)
Long-term core inventory					0		0
Contract assets, net					1,726,000	(8,773,000)	6,882,000
Other liabilities						1,904,000	295,000
Net cash used in operating activities					(644,000)	$ (6,409,000)	(8,148,000)
Historical Misapplication of GAAP Related to Timing of Recognizing Certain Expenses Incurred in Connection with New Business [Member]
Consolidated Statement of Cash Flow from Operating Activities [Abstract]
Net income (loss)		$ (5,495,000)	$ (2,650,000)	5,723,000	7,295,000		13,018,000	$ 10,368,000	$ 18,826,000	$ 38,776,000	$ 10,269,000
Deferred income taxes								(2,714,000)	1,495,000	6,865,000	(3,191,000)
Income tax receivable		(1,791,000)							(6,312,000)
Prepaid expenses and other current assets		(687,000)			366,000		(6,630,000)	(1,645,000)	(2,825,000)	(4,882,000)	3,383,000
Other assets		(51,000)			1,432,000		2,943,000	(163,000)	404,000	(4,364,000)	(1,795,000)
Accounts payable and accrued liabilities		10,868,000			(5,553,000)		(3,764,000)	(15,946,000)	(11,671,000)	12,447,000	6,918,000
Long-term core inventory								(38,361,000)	(46,978,000)	(25,245,000)	(53,006,000)
Contract assets, net		(841,000)
Other liabilities					2,185,000					(1,048,000)	1,377,000
Net cash used in operating activities		(924,000)			(644,000)		(8,148,000)	(9,803,000)	(13,944,000)	(5,269,000)	15,334,000
Historical Misapplication of GAAP Related to Timing of Recognizing Certain Expenses Incurred in Connection with New Business [Member] | As Previously Reported [Member]
Consolidated Statement of Cash Flow from Operating Activities [Abstract]
Net income (loss)		(5,014,000)	(6,806,000)	6,301,000	7,626,000		13,927,000	7,121,000	16,316,000	37,573,000	10,563,000
Deferred income taxes								(909,000)	3,055,000	6,510,000	(3,781,000)
Income tax receivable		(1,622,000)							(6,081,000)
Prepaid expenses and other current assets		(697,000)			421,000		(6,093,000)	(2,093,000)	(2,507,000)	(4,333,000)	2,765,000
Other assets		941,000			608,000		1,198,000	289,000	(384,000)	(3,339,000)	(477,000)
Accounts payable and accrued liabilities		11,117,000			(5,254,000)		(3,465,000)	(15,647,000)	(11,621,000)	12,446,000	6,620,000
Long-term core inventory								(37,222,000)	(45,839,000)	(24,964,000)	(53,408,000)
Contract assets, net		(2,722,000)
Other liabilities					2,324,000					(1,344,000)	1,673,000
Net cash used in operating activities		(924,000)			(644,000)		(8,148,000)	(9,803,000)	(13,944,000)	(5,269,000)	15,334,000
Historical Misapplication of GAAP Related to Timing of Recognizing Certain Expenses Incurred in Connection with New Business [Member] | Adjustment [Member]
Consolidated Statement of Cash Flow from Operating Activities [Abstract]
Net income (loss)		(481,000)	$ 4,156,000	$ (578,000)	(331,000)		(909,000)	3,247,000	2,510,000	1,203,000	(294,000)
Deferred income taxes								(1,805,000)	(1,560,000)	355,000	590,000
Income tax receivable		(169,000)							(231,000)
Prepaid expenses and other current assets		10,000			(55,000)		(537,000)	448,000	(318,000)	(549,000)	618,000
Other assets		(992,000)			824,000		1,745,000	(452,000)	788,000	(1,025,000)	(1,318,000)
Accounts payable and accrued liabilities		(249,000)			(299,000)		(299,000)	(299,000)	(50,000)	1,000	298,000
Long-term core inventory								(1,139,000)	(1,139,000)	(281,000)	402,000
Contract assets, net		1,881,000
Other liabilities					(139,000)					296,000	(296,000)
Net cash used in operating activities		$ 0			$ 0		$ 0	$ 0	$ 0	$ 0	$ 0