Minimum amount of other commitment not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in the taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.

No definition available.

Name:	us-gaap_OtherCommitment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Commitments and contingencies - Investment commitments (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Acquisition commitment
Other Commitments [Line Items]
Acquisition commitment percentage of ownership	100.00%
Equities \| Investment commitment
Other Commitments [Line Items]
Commitment, amount	$ 23.1	$ 26.4
Term loans \| Investment commitment
Other Commitments [Line Items]
Commitment, amount		$ 8.4