Subsequent events (Details) (Subsequent Event [Member], USD $) In Millions, except Per Share data, unless otherwise specified	0 Months Ended
	Feb. 28, 2015
Oaktree Capital Management [Member]
Subsequent Event [Line Items]
Ownership percentage of outstanding stock	68.80%
Merger agreement, per share amount used to determine number of shares at closing of merger agreement, conversion of outstanding loan principal	$ 1.50
OCM PE Holdings [Member]
Subsequent Event [Line Items]
Merger agreement, additional borrowings	$ 8.5
Number of days after merger agreement to receive funds	30 days
Investment, cash contribution less outstanding principal of loan at closing	$ 17.0
Merger agreement, per share amount used to determine number of shares at closing of merger agreement, conversion of outstanding loan principal	$ 1.50
Minimum [Member] | OCM PE Holdings [Member]
Subsequent Event [Line Items]
Ownership percentage of outstanding stock after conversion of loan to shares	80.00%