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MERCHANDISE TRUSTS - Contractual Maturities of Debt Securities Held in Merchandise Trusts (Detail) - Variable Interest Entity, Primary Beneficiary - Merchandise Trusts - Fixed maturities - USD ($)
$ in Thousands
Sep. 30, 2019
Dec. 31, 2018
Dec. 31, 2017
Investments Classified by Contractual Maturity Date [Line Items]      
Less than 1 year $ 208 $ 68 $ 76
1 year through 5 years 628 1,010 879
6 years through 10 years 264 163 179
More than 10 years 16 16 11
U.S. governmental securities      
Investments Classified by Contractual Maturity Date [Line Items]      
Less than 1 year 112    
1 year through 5 years 30 137 78
6 years through 10 years 246 108 54
More than 10 years 16    
Corporate debt securities      
Investments Classified by Contractual Maturity Date [Line Items]      
Less than 1 year 96 68 76
1 year through 5 years 598 873 801
6 years through 10 years $ 18 55 125
More than 10 years   $ 16 $ 11