The FASB and IASB have been working to create a common conceptual framework for financial reporting and the accounting information system which feeds financial reports.
The FASB stated in its publication Conceptual Framework for Financial Reporting: The Objective of Financial Reporting and Qualitative Characteristics and Constraints of Decision-Useful Financial Reporting Information(a FASB Exposure Draft):
A common goal of the Boards-a goal shared by their constituents-is for their standards to be clearly based on consistent principles. To be consistent, principles must be rooted in fundamental concepts rather than a collection of conventions.
Much of this framework relates to things like recognition and measurement concepts which are very important to the accounting information system as they impact the numbers that will turn up on a financial report. But, they are not really relevant to the notion of a financial report itself.
There are a number of things in the FASB/IASB framework which are directly related to financial reports. Let me point those out.
Objective of a financial report
First of, something of key importance is the objective of a financial report. To paraphrase, the objective of a financial report and financial reporting is to provide useful information to capital providers.
Financial statements
Phase Aof the conceptual framwork project defined financial statements a company would report as:
"Related disclosures" can be broken down further, basically a categorization of the disclosures, by the FASB accounting standards codification. I summarized the topics here and mapped the topics to the US GAAP taxonomy. I would venture to break "related disclosures" into the following based on the FASB accounting standards codification and the US GAAP Taxonomy:
Elements of financial statements
Financial statements are broken down into 10 elements by SFAC 6.
Other places have definitions of these elements of a financial statement such as here.
Seeing the "financial report schema"
It is looking more and more like there is a "financial report schema" hiding within US GAAP and IFRS. It seems to me that this schema is a basis for defining what a financial report looks like, somewhat of a blueprint. This blueprint or schema can be read by a computer software application to validate the semantics of the financial report. Humans use this schema today in the form of a disclosure checklist. But I believe that this schema can also be used by software applications to verify SEC XBRL financial filings.
Not only would SEC XBRL financial filings follow a schema, but the US GAAP Taxonomy should follow this schema also. The schema may be different for different industries. For example, the schema of a balance sheet is different for a classified balance sheet and an unclassified balance sheet. The schema is different for a single step income statement and a multi-step income statement. The schema is different for a partnership and corporation. But, financial reports are not random. They do have schemas.