Segment and geographic information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Segment and related information
Operating revenues	$ 167,610	$ 53,665
Segment assets	3,475,710	1,007,801	3,248,427
Project Adjusted EBITDA	92,851	35,993
Change in fair value of derivative instruments	58,422	(2,784)
Depreciation and amortization	49,945	17,437
Interest, net	8,868	6,240
Other project (income) expense	266	231
Project (loss) income	(24,650)	14,869
Administration	7,833	4,054
Interest, net	22,036	3,968
Foreign exchange loss (gain)	986	(658)
Income (loss) from operations before income taxes	(55,505)	7,505
Income tax expense (benefit)	(16,291)	1,523
Net (loss) income	(39,214)	5,982
North East
Segment and related information
Operating revenues	66,926	4,547
Segment assets	1,198,652	288,774
Project Adjusted EBITDA	42,398	7,488
Change in fair value of derivative instruments	58,016	490
Depreciation and amortization	17,447	4,596
Interest, net	4,738	2,434
Other project (income) expense	242	200
Project (loss) income	(38,045)	(232)
Income (loss) from operations before income taxes	(38,045)	(232)
Net (loss) income	(38,045)	(232)
South East
Segment and related information
Operating revenues	41,751	41,426
Segment assets	431,046	360,763
Project Adjusted EBITDA	21,674	19,588
Change in fair value of derivative instruments	406	(3,274)
Depreciation and amortization	9,372	9,434
Interest, net	169	309
Other project (income) expense	14	31
Project (loss) income	11,713	13,088
Income (loss) from operations before income taxes	11,713	13,088
Net (loss) income	11,713	13,088
North West
Segment and related information
Operating revenues	15,300
Segment assets	825,138	47,156
Project Adjusted EBITDA	13,439	866
Depreciation and amortization	10,426	439
Interest, net	1,096	370
Other project (income) expense	7
Project (loss) income	1,910	57
Income (loss) from operations before income taxes	1,910	57
Net (loss) income	1,910	57
South West
Segment and related information
Operating revenues	42,696	7,644
Segment assets	940,675	226,542
Project Adjusted EBITDA	18,764	8,501
Depreciation and amortization	12,657	2,961
Interest, net	2,808	3,089
Other project (income) expense	82
Project (loss) income	3,217	2,451
Income (loss) from operations before income taxes	3,217	2,451
Net (loss) income	3,217	2,451
Un-allocated Corporate
Segment and related information
Operating revenues	937	48
Segment assets	80,199	84,566
Project Adjusted EBITDA	(3,424)	(450)
Depreciation and amortization	43	7
Interest, net	57	38
Other project (income) expense	(79)
Project (loss) income	(3,445)	(495)
Administration	7,833	4,054
Interest, net	22,036	3,968
Foreign exchange loss (gain)	986	658
Income (loss) from operations before income taxes	(34,300)	(7,859)
Income tax expense (benefit)	(16,291)	1,523
Net (loss) income	$ (18,009)	$ (9,382)