Assets Held for Development (Summary) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Assets Held for Development [Line Items]
Assets held for development	$ 1,090,198	$ 1,089,819
Land | Echelon Infrastructure
Assets Held for Development [Line Items]
Assets held for development	215,969	215,969
Construction and Development Costs | Echelon Infrastructure
Assets Held for Development [Line Items]
Assets held for development	501,166	500,787
Construction and Development Costs | Echelon Central Energy Facility
Assets Held for Development [Line Items]
Assets held for development	163,806	163,806
Project Management and Other Costs | Echelon Infrastructure
Assets Held for Development [Line Items]
Assets held for development	115,712	115,712
Professional and Design Fees | Echelon Infrastructure
Assets Held for Development [Line Items]
Assets held for development	$ 93,545	$ 93,545