Variable interest entities and securitization activities - Assets of Unconsolidated VIEs (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Carrying amount
Mortgage-backed securities	$ 27,436	$ 32,041
Investment in unconsolidated joint ventures	133,321	118,641
Total Assets	12,441,217	11,620,977
Unconsolidated VIEs
Carrying amount
Mortgage-backed securities	26,301	24,408
Investment in unconsolidated joint ventures	133,321	118,641
Total Assets	159,622	143,049
Maximum Exposure to Loss
Mortgage backed securities, at fair value	26,301	24,408
Investment in unconsolidated joint venture	133,321	118,641
Total assets in unconsolidated VIEs maximum exposure to loss	$ 159,622	$ 143,049