Fair Value of Financial Instruments - Valuation Method Of Level 3 Financial Instruments Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial mortgage loans, held-for-sale, measured at fair value	$ 91,813	$ 112,562
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial mortgage loans, held-for-sale, measured at fair value	91,813	112,562
Fair Value, Measurements, Recurring | Level III
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial mortgage loans, held-for-sale, measured at fair value	91,813	112,562
Other real estate investments, measured at fair value	2,496	2,557
Commercial mortgage loans, held-for-sale, measured at fair value | Fair Value, Measurements, Recurring | Level III
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial mortgage loans, held-for-sale, measured at fair value	$ 91,813	$ 112,562
Discounted Cash Flow | Weighted Average | Commercial mortgage loans, held-for-sale, measured at fair value | Fair Value, Measurements, Recurring | Level III
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Yield	4.20%	4.90%
Discounted Cash Flow | Weighted Average | Other real estate investments, measured at fair value | Fair Value, Measurements, Recurring | Level III
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Yield	13.40%	12.40%
Discounted Cash Flow | Minimum | Commercial mortgage loans, held-for-sale, measured at fair value | Fair Value, Measurements, Recurring | Level III
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Yield	2.40%	4.70%
Discounted Cash Flow | Minimum | Other real estate investments, measured at fair value | Fair Value, Measurements, Recurring | Level III
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Yield	12.40%	11.40%
Discounted Cash Flow | Maximum | Commercial mortgage loans, held-for-sale, measured at fair value | Fair Value, Measurements, Recurring | Level III
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Yield	5.60%	5.20%
Discounted Cash Flow | Maximum | Other real estate investments, measured at fair value | Fair Value, Measurements, Recurring | Level III
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Yield	14.40%	13.40%