Impact on Previously Issued Financial Statements for the Correction of an Error, Revised Consolidated Statement of Comprehensive Income (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 Comprehensive Income [Abstract]
Net income (loss)	$ 3,513,000			$ 5,595,000	$ 7,820,000	$ (1,982,000)	$ 13,415,000
Comprehensive income (loss)	$ 3,511,000			6,263,000		$ (2,699,000)	14,368,000
Historical Misapplication of GAAP Related to Timing of Recognizing Certain Expenses Incurred in Connection with New Business [Member]
Consolidated Statement of Comprehensive Income [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
Comprehensive income (loss)		(6,210,000)	(2,320,000)	6,391,000	7,580,000		13,971,000	11,651,000	20,839,000	36,187,000	7,935,000
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 Comprehensive Income [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
Comprehensive income (loss)		(5,729,000)	(6,476,000)	6,969,000	7,911,000		14,880,000	8,404,000	18,329,000	34,984,000	8,229,000
Historical Misapplication of GAAP Related to Timing of Recognizing Certain Expenses Incurred in Connection with New Business [Member] | Adjustment [Member]
Consolidated Statement of Comprehensive Income [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)
Comprehensive income (loss)		$ (481,000)	$ 4,156,000	$ (578,000)	$ (331,000)		$ (909,000)	$ 3,247,000	$ 2,510,000	$ 1,203,000	$ (294,000)