Provision for income taxes (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax [Line Items]
Pre-Tax (Loss)/Income	$ (14,992)	$ 8,101	$ (4,637)
Current	17,169	20,196	20,649
Deferred	459	1,455	(1,038)
Provision for income taxes	17,628	21,651	19,611
Bermuda
Income Tax [Line Items]
Pre-Tax (Loss)/Income	(17,696)	(8,244)	(23,436)
Current	0	0	0
Deferred	0	0	0
Provision for income taxes	0	0	0
United States
Income Tax [Line Items]
Pre-Tax (Loss)/Income	(3,955)	1,903	13,918
Current	(369)	3,656	3,986
Deferred	100	(647)	(561)
Provision for income taxes	(269)	3,009	3,425
Rest of the world
Income Tax [Line Items]
Pre-Tax (Loss)/Income	6,659	14,442	4,881
Current	17,538	16,540	16,663
Deferred	359	2,102	(477)
Provision for income taxes	$ 17,897	$ 18,642	$ 16,186