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Investments (Real Estate Investments) - Additional Information (Detail) - USD ($) $ in Thousands		1 Months Ended		12 Months Ended
	Jun. 13, 2018	Oct. 17, 2017	Aug. 16, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Nov. 30, 2018
Schedule of Investments [Line Items]
Commercial real estate purchase price	$ 6,766	$ 9,100	$ 12,250
Acquisition related costs		$ 115
Depreciation and amortization expenses under real estate investments				$ 1,369	$ 1,238	$ 1,272
Commercial real estate acquisition assumed liabilities	$ 35
Assets held for sale				9,810
Real Estate Investments [Member]
Schedule of Investments [Line Items]
Depreciation and amortization expenses under real estate investments				$ 1,536	$ 1,447	$ 531
Assets held for sale							$ 9,810