Significant Accounting Policies - Additional Information (Detail) - USD ($)		6 Months Ended		12 Months Ended
	Jun. 15, 2018	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017		Feb. 25, 2015	Feb. 10, 2014	May 22, 2012
Significant Accounting Policies [Line Items]
Plan Effective Date		Mar. 19, 2012
Unearned premiums		$ 0		$ 39,000	[1]
Premium deficiency reserves		300,000		300,000
Other assets		4,970,000		558,000	[1]
Deferred offering costs		4,600,000
Prepaid non-debt related expenses		400,000		600,000
Other liabilities		20,586,000		16,303,000	[1]
Accrued professional fees		12,300,000		$ 4,700,000
Comprehensive income		$ 0
Income tax at the federal statutory rate		21.00%		35.00%
Amount of dividends paid on or after Effective Date		$ 0
Preferred stock dividends paid		1,000,000	$ 9,000,000
2012 Plan [Member]
Significant Accounting Policies [Line Items]
Common stock reserved for future issuance						12,000,000	3,000,000	2,000,000
Redeemable Convertible Series B Preferred Stock [Member]
Significant Accounting Policies [Line Items]
Accrued fees		8,300,000		$ 8,300,000
Accrued fees for extension of escrow agreement				2,500,000
Accrued cash dividends				800,000
Additional accrued preferred stock dividends		0		800,000
Common stock issued to satisfy dividends earned, shares	9,652,268
Common stock issued to satisfy dividends earned, value	$ 12,900,000
Preferred stock dividends paid		$ 1,000,000		$ 18,000,000

[1] Balances derived from audited financial statements as of December 31, 2017.