Intangible Assets Subject to Amortization - Finite-Lived Intangible Assets (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Intangible Assets Subject to Amortization
Balance at the beginning of the period	$ 1.7	$ 1.9
Acquisitions		0.2
Amortization	(0.4)	(0.4)	$ (0.9)
Balance at the end of the period	$ 1.3	$ 1.7	$ 1.9