Fair value measurements (Summary of Valuation Techniques and Significant Unobservable Inputs Used) (Details) - Fair Value, Inputs, Level 3 [Member] - Recurring [Member] - Warrant [Member] - Black-Scholes formulation [Member]	Mar. 31, 2025 USD ($) Y $ / shares	Dec. 31, 2024 Y USD ($)
Minimum [Member] | Unobservable Inputs, Stock Price [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Warrants, Range of Input Values	0.01	0.0001
Minimum [Member] | Unobservable Inputs, Exercise Price [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Warrants, Range of Input Values	0.0002	0.0002
Minimum [Member] | Unobservable Inputs, Time to Maturity (in Years) [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Warrants, Range of Input Values | Y	2.66	2.91
Minimum [Member] | Unobservable Inputs, Annualized Volatility [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Warrants, Range of Input Values	0.4051	0.47
Maximum [Member] | Unobservable Inputs, Stock Price [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Warrants, Range of Input Values	0.1414	0.1414
Maximum [Member] | Unobservable Inputs, Exercise Price [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Warrants, Range of Input Values	0.09	0.09
Maximum [Member] | Unobservable Inputs, Time to Maturity (in Years) [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Warrants, Range of Input Values | Y	6.69	6.94
Maximum [Member] | Unobservable Inputs, Annualized Volatility [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Warrants, Range of Input Values	0.7315	0.73
Weighted Average [Member] | Unobservable Inputs, Stock Price [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Warrants, Range of Input Values	(0.0007)	(0.0007)
Weighted Average [Member] | Unobservable Inputs, Exercise Price [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Warrants, Range of Input Values	(0.0007)	(0.0007)
Weighted Average [Member] | Unobservable Inputs, Time to Maturity (in Years) [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Warrants, Range of Input Values | Y	(2.8)	(3.05)
Weighted Average [Member] | Unobservable Inputs, Annualized Volatility [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Warrants, Range of Input Values	(0.7296)	(0.7285)