Nature of Operations (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2016 USD ($) agreement	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Liquidity
Net loss attributable to common shareholders	$ 11,780	$ 11,077	$ 55,800	$ 88,600	$ 62,800
Accumulated deficit	1,005,656		993,876
Net cash used in operating activities	6,916	13,645
Net loss attributable to the Company	(11,754)	(11,051)
Net inflows of noncash operating assets and liabilities	3,200
Cash and cash equivalents	66,882	$ 131,537	63,961	$ 146,205
Net working capital	62,800		88,500
Cash added to the restricted accounts	$ 0		$ 14,200
Number of power purchase agreements | agreement	7
Remaining lease payment	$ 58,862
Power purchase agreements
Liquidity
Remaining lease payment	24,900
Master Lease
Liquidity
Minimum level of unrestricted cash	$ 50,000
Number of years that the underlying assets not be deployed	5 years
Residual exposure	$ 12,100
Secured term loan facility | Minimum
Liquidity
Cash and cash equivalents	$ 25,000