Operating loss carryforwards (Details) - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating Loss Carryforwards [Line Items]
Capital loss carryforward	$ 10.6	$ 12.9
Capital loss carryforward, expiration date	Mar. 31, 2020
Capital loss carryforward, valuation allowance	$ 10.4
Foreign Tax Authority and Federal and State Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	101.1
Operating loss carryforwards, valuation allowance	$ 74.6
Minimum | Foreign Tax Authority and Federal and State Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, expiration date	Mar. 31, 2018
Maximum | Foreign Tax Authority and Federal and State Jurisdiction
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, expiration date	Mar. 31, 2037