Summary of Significant Accounting Policies (Details 5)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)	Dec. 31, 2011 Swedish kronor SEK	Dec. 31, 2011 Swedish kronor Beginning of period SEK	Dec. 31, 2010 Swedish kronor Beginning of period SEK	Dec. 31, 2011 Swedish kronor End of period SEK	Dec. 31, 2010 Swedish kronor End of period SEK	Dec. 31, 2011 British pound Beginning of period GBP (£)	Dec. 31, 2010 British pound Beginning of period GBP (£)	Dec. 31, 2011 British pound End of period GBP (£)	Dec. 31, 2010 British pound End of period GBP (£)	Dec. 31, 2011 Canadian dollar Beginning of period CAD	Dec. 31, 2010 Canadian dollar Beginning of period CAD	Dec. 31, 2011 Canadian dollar End of period CAD	Dec. 31, 2010 Canadian dollar End of period CAD
Summary of Significant Accounting Policies
Unrealized foreign currency translation gains	$ 46,100,000	$ 61,400,000
Rates of exchange for the U.S. dollar
Exchange rate			6.86	6.7030	7.1280	6.8645	6.7030	£ 0.6420	£ 0.6191	£ 0.6434	£ 0.6420	0.9981	1.0485	1.0193	0.9981