Fair Value of Financial Instruments - Narrative (Details) - Level 2 - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Market Approach Valuation Technique | Junior subordinated notes
Financial Instruments Not Measured at Fair Value
Market interest rate (as a percent)	7.61%	7.79%
Market Approach Valuation Technique | Mortgages | Minimum
Financial Instruments Not Measured at Fair Value
Market interest rate (as a percent)	3.56%	3.94%
Market Approach Valuation Technique | Mortgages | Maximum
Financial Instruments Not Measured at Fair Value
Market interest rate (as a percent)	5.33%	5.61%
Carrying and Fair Value | Junior subordinated notes
Financial Instruments Not Measured at Fair Value
Estimated fair value (lower) higher than carrying value	$ 11,978	$ 11,974
Carrying and Fair Value | Mortgages
Financial Instruments Not Measured at Fair Value
Estimated fair value (lower) higher than carrying value	$ 8,096	$ 19,334