Significant Accounting Policies and New Accounting Pronouncements (Policies)	3 Months Ended
Mar. 31, 2017
Accounting Policies [Abstract]
New Accounting Pronouncements Issued	The following are new accounting pronouncements issued since December 31, 2016, that we are evaluating to determine their effect on our condensed consolidated interim financial statements. (a) Clarifying the definition of a business and the scope of asset derecognition guidance, and accounting for partial sales of nonfinancial assets The Financial Accounting Standards Board (FASB) issued amendments in January 2017 to clarify the definition of a business, and in a second phase of the project, issued amendments in February 2017 concerning asset derecognition and partial sales of nonfinancial assets. The revised definition of a business sets out a new framework for a company to apply in classifying transactions as acquisitions (or disposals) of assets versus businesses. According to the revised definition, an integrated set of activities and assets is a business if it has at a minimum, an input and a substantive process that together significantly contribute to the ability to create outputs. The definition of outputs is narrowed and aligned with how outputs are described in Accounting Standards Codification, Topic 606, Revenue From Contracts With Customers (ASC 606). The amendments create a two-step method for assessing whether a transaction is an acquisition (disposal) of assets or a business. A set would not be a business when substantially all of the fair value of the gross assets acquired (disposed) is concentrated in a single identifiable asset or group of similar identifiable assets. Fewer transactions are expected to involve acquiring or selling a business as a result of the amendments. The amendments issued in February 2017 clarify the scope of asset derecognition guidance and accounting for partial sales of nonfinancial assets, and also define in-substance nonfinancial assets. Those amendments apply to a company that: sells nonfinancial assets (land, buildings, materials and supplies, intangible assets) to noncustomers; sells nonfinancial assets and financial assets (cash, receivables) when the value is concentrated in the nonfinancial assets; or sells partial ownership interests in nonfinancial assets. The amendments do not apply to sales to customers or to sales of businesses. The new guidance in ASC 610-20 on accounting for derecognition of a nonfinancial asset and an in-substance nonfinancial asset applies only when the asset (or asset group) does not meet the definition of a business and is not a not-for-profit activity. The amendments issued in both January 2017 and February 2017 as described above are effective for public entities for annual and interim periods in fiscal years beginning after December 15, 2017, with early adoption permitted. We do not plan to early adopt. For the amendments concerning the definition of a business, an entity should apply the amendments prospectively on or after the effective date. For the amendments concerning asset derecognition and partial sales of nonfinancial assets an entity must apply them at the same time that it applies the new ASC 606 revenue recognition standard and may elect to apply the amendments retrospectively following either a full retrospective approach or a modified retrospective approach, but does not have to apply the same transition method as for ASC 606. Regardless of which transition method an entity applies to contracts with noncustomers, such as transactions within the scope of ASC 610-20, it must apply the amended definition of a business to those contracts. We expect the amendments issued in both January 2017 and February 2017 will affect our accounting for tax equity investments, which we expect to classify as noncontrolling interests in accordance with ASC 606. We are currently evaluating how our adoption of the amendments will affect our results of operations, financial position, cash flows, and disclosures. (b) Improving the presentation of net periodic benefit costs In March 2017 the FASB issued amendments to improve the presentation of net periodic pension cost and net periodic postretirement benefit cost in the financial statements. The amendments require an entity to present service cost separately from the other components of net benefit cost, and to report the service cost component in the income statement line item(s) where it reports the corresponding compensation cost. An entity is to present all other components of net benefit cost outside of operating cost, if it presents that subtotal. The amendments also allow only the service cost component to be eligible for capitalization when applicable (for example, as a cost of a self-constructed asset). The amendments are effective for public entities for annual and interim periods in fiscal years beginning after December 15, 2017, with early adoption permitted. We do not plan to early adopt. An entity is required to apply the amendments retrospectively for the presentation of the service cost component and the other components of net periodic pension cost and net periodic postretirement benefit cost in the income statement and prospectively, on and after the effective date, for the capitalization of the service cost component of net periodic pension cost and net periodic postretirement benefit in assets. A practical expedient allows an entity to retrospectively apply the amendments on adoption to net benefit costs for comparative periods by using the amounts disclosed in the notes to financial statements for pension and postretirement benefit plans for those periods. We are currently evaluating how our adoption of the amendments will affect our results of operations, financial position, cash flows, and disclosures.

The following are new accounting pronouncements issued since December 31, 2016, that we are evaluating to determine their effect on our condensed consolidated interim financial statements.

(a) Clarifying the definition of a business and the scope of asset derecognition guidance, and accounting for partial sales of nonfinancial assets

The Financial Accounting Standards Board (FASB) issued amendments in January 2017 to clarify the definition of a business, and in a second phase of the project, issued amendments in February 2017 concerning asset derecognition and partial sales of nonfinancial assets. The revised definition of a business sets out a new framework for a company to apply in classifying transactions as acquisitions (or disposals) of assets versus businesses. According to the revised definition, an integrated set of activities and assets is a business if it has at a minimum, an input and a substantive process that together significantly contribute to the ability to create outputs. The definition of outputs is narrowed and aligned with how outputs are described in Accounting Standards Codification, Topic 606, Revenue From Contracts With Customers (ASC 606). The amendments create a two-step method for assessing whether a transaction is an acquisition (disposal) of assets or a business. A set would not be a business when substantially all of the fair value of the gross assets acquired (disposed) is concentrated in a single identifiable asset or group of similar identifiable assets. Fewer transactions are expected to involve acquiring or selling a business as a result of the amendments.

The amendments issued in February 2017 clarify the scope of asset derecognition guidance and accounting for partial sales of nonfinancial assets, and also define in-substance nonfinancial assets. Those amendments apply to a company that: sells nonfinancial assets (land, buildings, materials and supplies, intangible assets) to noncustomers; sells nonfinancial assets and financial assets (cash, receivables) when the value is concentrated in the nonfinancial assets; or sells partial ownership interests in nonfinancial assets. The amendments do not apply to sales to customers or to sales of businesses. The new guidance in ASC 610-20 on accounting for derecognition of a nonfinancial asset and an in-substance nonfinancial asset applies only when the asset (or asset group) does not meet the definition of a business and is not a not-for-profit activity.

The amendments issued in both January 2017 and February 2017 as described above are effective for public entities for annual and interim periods in fiscal years beginning after December 15, 2017, with early adoption permitted. We do not plan to early adopt. For the amendments concerning the definition of a business, an entity should apply the amendments prospectively on or after the effective date. For the amendments concerning asset derecognition and partial sales of nonfinancial assets an entity must apply them at the same time that it applies the new ASC 606 revenue recognition standard and may elect to apply the amendments retrospectively following either a full retrospective approach or a modified retrospective approach, but does not have to apply the same transition method as for ASC 606. Regardless of which transition method an entity applies to contracts with noncustomers, such as transactions within the scope of ASC 610-20, it must apply the amended definition of a business to those contracts. We expect the amendments issued in both January 2017 and February 2017 will affect our accounting for tax equity investments, which we expect to classify as noncontrolling interests in accordance with ASC 606. We are currently evaluating how our adoption of the amendments will affect our results of operations, financial position, cash flows, and disclosures.

(b) Improving the presentation of net periodic benefit costs

In March 2017 the FASB issued amendments to improve the presentation of net periodic pension cost and net periodic postretirement benefit cost in the financial statements. The amendments require an entity to present service cost separately from the other components of net benefit cost, and to report the service cost component in the income statement line item(s) where it reports the corresponding compensation cost. An entity is to present all other components of net benefit cost outside of operating cost, if it presents that subtotal. The amendments also allow only the service cost component to be eligible for capitalization when applicable (for example, as a cost of a self-constructed asset). The amendments are effective for public entities for annual and interim periods in fiscal years beginning after December 15, 2017, with early adoption permitted. We do not plan to early adopt. An entity is required to apply the amendments retrospectively for the presentation of the service cost component and the other components of net periodic pension cost and net periodic postretirement benefit cost in the income statement and prospectively, on and after the effective date, for the capitalization of the service cost component of net periodic pension cost and net periodic postretirement benefit in assets. A practical expedient allows an entity to retrospectively apply the amendments on adoption to net benefit costs for comparative periods by using the amounts disclosed in the notes to financial statements for pension and postretirement benefit plans for those periods. We are currently evaluating how our adoption of the amendments will affect our results of operations, financial position, cash flows, and disclosures.