XML 43 R31.htm IDEA: XBRL DOCUMENT v3.19.1
Summary Information Concerning Indebtedness (Parenthetical) (Detail) - USD ($)
Mar. 31, 2019
Dec. 31, 2018
Debt Instrument [Line Items]    
Outstanding Principal $ 996,508,000 $ 991,415,000
Unsecured Credit Facility    
Debt Instrument [Line Items]    
Credit facility borrowing capacity 300,000,000 300,000,000
Outstanding Principal $ 111,743,000 [1] $ 155,743,000 [2]
[1] The unsecured credit facility total capacity is $300,000, of which $111,743 was outstanding as of March 31, 2019.
[2] The unsecured credit facility total capacity was $300,000, of which $155,743 was outstanding as of December 31, 2018.