Fair Value of Financial Instruments - Narrative (Details) - Level 2 - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018
Market Approach Valuation Technique | Junior subordinated notes
Financial Instruments Not Measured at Fair Value
Market interest rate (as a percent)	7.79%	7.35%
Market Approach Valuation Technique | Mortgages | Minimum
Financial Instruments Not Measured at Fair Value
Market interest rate (as a percent)	3.94%	4.30%
Market Approach Valuation Technique | Mortgages | Maximum
Financial Instruments Not Measured at Fair Value
Market interest rate (as a percent)	5.61%	6.04%
Carrying and Fair Value | Junior subordinated notes
Financial Instruments Not Measured at Fair Value
Estimated fair value (lower) higher than carrying value	$ 11,974	$ 12,451
Carrying and Fair Value | Mortgages
Financial Instruments Not Measured at Fair Value
Estimated fair value (lower) higher than carrying value	$ 19,334	$ 34,039