Stock incentive plan and share-based compensation (Details)			9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2012 All Option Plans [Member] USD ($)	Sep. 30, 2012 All Option Plans [Member] GBP (£)
Number of Shares,Outstanding at December 31, 2011	6	6	11	11
Number of Shares,Granted			0	0
Number of Shares,Exercised			0	0
Number of Shares,Forfeited/ Cancelled			(5)	(5)
Number of Shares,Outstanding at September 30, 2012	6	6	6	6
Weighted-Average Exercise Price,Outstanding at December 31, 2011			$ 58,500	£ 35,700
Weighted-Average Exercise Price,Granted			$ 0
Weighted-Average Exercise Price,Exercised			$ 0
Weighted-Average Exercise Price, Forfeited/Cancelled			$ 30,917	£ 19,500
Weighted-Average Exercise Price,Outstanding at September 30, 2012			$ 46,326	£ 29,250
Number of shares Exercisable at December 31, 2011			10	10
Number of shares Exercisable at September 30, 2012			6	6
Weighted-Average Exercise Price, Exercisable at December 31, 2011			$ 58,500	£ 35,700
Weighted-Average Exercise Price, Exercisable at September 30, 2012			$ 46,326	£ 29,250