Derivative Instruments - Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Due to Counterparties
Interest rate swaps and interest rate swaptions
Collateral already posted, aggregate fair value	$ 16.3	$ 0.0
Due From Counterparties
Interest rate swaps and interest rate swaptions
Collateral already posted, aggregate fair value	27.1	$ 55.4
Interest rate swaps | Fixed Pay Rate
Interest rate swaps and interest rate swaptions
Derivative, terminated	3,100.0
Interest rate swaps | Variable Pay Rate
Interest rate swaps and interest rate swaptions
Derivative, terminated	$ 1,900.0