Regulatory and legal developments - Gain Contingency (Details) (Subsequent Event, USD $) In Millions, unless otherwise specified	0 Months Ended
	Jul. 22, 2014
Positive Outcome of Litigation
Gain Contingencies [Line Items]
Litigation settlement	$ 9.70
Damages set aside	15.0
Failure To Comply Damages
Gain Contingencies [Line Items]
Litigation settlement	1.60
Unfair and Deceptive Acts Damages
Gain Contingencies [Line Items]
Litigation settlement	4.80
Exemplary Damages
Gain Contingencies [Line Items]
Litigation settlement	$ 15.00