Loss on extinguishment of debt (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Loss on extinguishment of debt
Premiums paid on redemption / repurchase of 8.875% Senior Notes		$ 28,572		$ 1,770
Deferred charges written off		8,125	599	3,091
Total	$ 36,697	$ 36,697	$ 599	$ 4,861