Accounting standards	12 Months Ended
Dec. 31, 2017
Accounting Standards [Abstract]
Accounting standards	3. Accounting standards A. New standards and interpretations not yet adopted A number of new standards and amendments to existing standards are not yet effective for the year ended December 31, 2017, and have not been applied in preparing these consolidated financial statements. Cameco does not intend to early adopt any of the following standards or amendments to existing standards, unless otherwise noted. i. Revenue In May 2014, the International Accounting Standards Board (IASB) issued IFRS 15, Revenue from Contracts with Customers (IFRS 15). IFRS 15 is effective for periods beginning on or after January 1, 2018 and is to be applied retrospectively. IFRS 15 clarifies the principles for recognizing revenue from contracts with customers. Our assessment primarily involved reviewing our sales contracts to determine if any performance obligations exist that will need to be separately identified that may affect the timing of when revenue will be recognized under IFRS 15. Based on our assessment, Cameco has not identified any material impacts on the timing and measurement of revenue from our existing revenue recognition practices from the adoption of the new standard, however we do expect to have additional disclosures. ii. Financial instruments In July 2014, the IASB issued IFRS 9, Financial Instruments (IFRS 9). IFRS 9 replaces the existing guidance in IAS 39, Financial Instruments: Recognition and Measurement (IAS 39). IFRS 9 includes revised guidance on the classification and measurement of financial assets, a new expected credit loss model for calculating impairment on financial assets and new hedge accounting requirements. It also carries forward, from IAS 39, guidance on recognition and derecognition of financial instruments. IFRS 9 is effective for annual periods beginning on or after January 1, 2018, with early adoption of the new standard permitted. Cameco does not apply hedge accounting and does not currently intend to apply hedge accounting upon adoption of IFRS 9. Based on our assessment, we do not expect adoption of the standard to have a material impact on the financial statements, however we do expect to have additional disclosures. iii. Leases In January 2016, the IASB issued IFRS 16, Leases (IFRS 16). IFRS 16 is effective for periods beginning on or after January 1, 2019, with early adoption permitted. IFRS 16 eliminates the current dual model for lessees, which distinguishes between on-balance sheet finance leases and off-balance sheet operating leases. Instead, there is a single, on-balance sheet accounting model that is similar to current finance lease accounting. The extent of the impact of adoption of IFRS 16 has not yet been determined. iv. Income tax In June 2017, the IASB issued IFRIC 23, Uncertainty over Income Tax Treatments (IFRIC 23). IFRIC 23 is effective for periods beginning on or after January 1, 2019 with early adoption permitted. IFRIC 23 provides guidance on the accounting for current and deferred tax liabilities and assets in circumstances in which there is uncertainty over income tax treatments. The extent of the impact of the adoption of IFRIC 23 has not yet been determined.

3. Accounting standards

A. New standards and interpretations not yet adopted

A number of new standards and amendments to existing standards are not yet effective for the year ended December 31, 2017, and have not been applied in preparing these consolidated financial statements. Cameco does not intend to early adopt any of the following standards or amendments to existing standards, unless otherwise noted.

i. Revenue

In May 2014, the International Accounting Standards Board (IASB) issued IFRS 15, Revenue from Contracts with Customers (IFRS 15). IFRS 15 is effective for periods beginning on or after January 1, 2018 and is to be applied retrospectively. IFRS 15 clarifies the principles for recognizing revenue from contracts with customers. Our assessment primarily involved reviewing our sales contracts to determine if any performance obligations exist that will need to be separately identified that may affect the timing of when revenue will be recognized under IFRS 15. Based on our assessment, Cameco has not identified any material impacts on the timing and measurement of revenue from our existing revenue recognition practices from the adoption of the new standard, however we do expect to have additional disclosures.

ii. Financial instruments

In July 2014, the IASB issued IFRS 9, Financial Instruments (IFRS 9). IFRS 9 replaces the existing guidance in IAS 39, Financial Instruments: Recognition and Measurement (IAS 39). IFRS 9 includes revised guidance on the classification and measurement of financial assets, a new expected credit loss model for calculating impairment on financial assets and new hedge accounting requirements. It also carries forward, from IAS 39, guidance on recognition and derecognition of financial instruments.

IFRS 9 is effective for annual periods beginning on or after January 1, 2018, with early adoption of the new standard permitted. Cameco does not apply hedge accounting and does not currently intend to apply hedge accounting upon adoption of IFRS 9. Based on our assessment, we do not expect adoption of the standard to have a material impact on the financial statements, however we do expect to have additional disclosures.

iii. Leases

In January 2016, the IASB issued IFRS 16, Leases (IFRS 16). IFRS 16 is effective for periods beginning on or after January 1, 2019, with early adoption permitted. IFRS 16 eliminates the current dual model for lessees, which distinguishes between on-balance sheet finance leases and off-balance sheet operating leases. Instead, there is a single, on-balance sheet accounting model that is similar to current finance lease accounting. The extent of the impact of adoption of IFRS 16 has not yet been determined.

iv. Income tax

In June 2017, the IASB issued IFRIC 23, Uncertainty over Income Tax Treatments (IFRIC 23). IFRIC 23 is effective for periods beginning on or after January 1, 2019 with early adoption permitted. IFRIC 23 provides guidance on the accounting for current and deferred tax liabilities and assets in circumstances in which there is uncertainty over income tax treatments. The extent of the impact of the adoption of IFRIC 23 has not yet been determined.