Commitments, Contingencies and Off-Balance Sheet Arrangements - Off-Balance Sheet Commitments (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($)
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Amount of Commitment Expiration by Period - 2020	$ 0.2
Amount of Commitment Expiration by Period - 2021	0.2
Amount of Commitment Expiration by Period - 2022	0.2
Amount of Commitment Expiration by Period - 2023	0.2
Amount of Commitment Expiration by Period - 2024	0.2
Amount of Commitment Expiration by Period - Thereafter	17.5
Total Amounts Committed	18.5
Letters of Credit [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Amount of Commitment Expiration by Period - Thereafter	17.1
Total Amounts Committed	17.1
Financial Guarantees [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Amount of Commitment Expiration by Period - 2020	0.2
Amount of Commitment Expiration by Period - 2021	0.2
Amount of Commitment Expiration by Period - 2022	0.2
Amount of Commitment Expiration by Period - 2023	0.2
Amount of Commitment Expiration by Period - 2024	0.2
Amount of Commitment Expiration by Period - Thereafter	0.4
Total Amounts Committed	$ 1.4