Derivative instruments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Notional Amount	$ 638,667	$ 530,354
Asset Derivatives Fair Value	36,812	54,352
Asset Derivatives Fair Value	36,812	54,352
Liabilities Derivatives Fair Value	(212)	$ (1,319)
Derivative gain (loss)
Net Realized Gain (Loss)	$ 20,847
Net Realized gain (loss) - Statement of Income	Realized Investment Gains (Losses)	Realized Investment Gains (Losses)
Unrealized Gain (Loss)	$ (17,498)	$ 50,180
Unrealized gain (loss) - Statement of Income	Net unrealized gain (loss) on financial instruments	Net unrealized gain (loss) on financial instruments
Total change in OCI for period	$ (10,533)	$ (2,133)	$ 2,539
Designated as Hedging
Derivative gain (loss)
Derivatives - effective portion reclassified from AOCI to income	(1,168)	(1,412)
Total income statement impact	(1,168)	(1,412)
Derivatives- effective portion recorded in OCI	(11,701)	(3,545)
Total change in OCI for period	(10,533)	(2,133)
Interest Rate Swaps
Asset Derivatives Fair Value	36,812	53,229
Derivative gain (loss)
Net Realized Gain (Loss)	20,116	9,701
Unrealized Gain (Loss)	(17,482)	50,982
Interest Rate Swaps | Not Designated as Hedging | Interest Rate Risk
Notional Amount	183,081	216,381
Asset Derivatives Fair Value	12,349	19,366
Interest Rate Swaps | Designated as Hedging | Interest Rate Risk
Notional Amount	416,139	266,139
Asset Derivatives Fair Value	24,463	33,863
TBA agency securities
Liabilities Derivatives Fair Value	(212)	(1,319)
FX forwards
Asset Derivatives Fair Value		1,123
Derivative gain (loss)
Net Realized Gain (Loss)	731	3,548
Unrealized Gain (Loss)	(16)	(802)
FX forwards | Foreign Exchange Rate Risk
Notional Amount	39,447	47,834
Asset Derivatives Fair Value		1,123
Liabilities Derivatives Fair Value	$ (212)	$ (1,319)