XML 90 R63.htm IDEA: XBRL DOCUMENT v3.8.0.1
Investments (Aggregated Income Statement Summarized Financial Information for Partnerships in our Alternative Investment Portfolio) (Details) - USD ($)
$ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2017
Dec. 31, 2016
Sep. 30, 2016
Dec. 31, 2015
Sep. 30, 2015
Sep. 30, 2014
Schedule of Equity Method Investments [Line Items]                            
Net investment income earned $ 42,587 $ 40,446 $ 41,430 $ 37,419 $ 35,428 $ 33,375 $ 31,182 $ 30,769 $ 161,882 $ 130,754   $ 121,316    
Investments Accounted For Under The Equity Method [Member]                            
Schedule of Equity Method Investments [Line Items]                            
Net investment (loss) income                     $ (143,000)   $ (44,000) $ 129,000
Realized gains                     325,000   1,374,000 1,187,000
Net change in unrealized appreciation (depreciation)                     2,894,000   (719,000) (1,364,000)
Net Income                     $ 3,076,000   $ 611,000 $ (48,000)
Alternative Investments [Member]                            
Schedule of Equity Method Investments [Line Items]                            
Net investment income earned                 $ 12,700 $ 3,100   $ (1,900)