xbrl us gaap contextRef standard?

[rdunksgok]

Please tell me this is standardized, or at least there is some way to decipher it.I'm looking at these 3 random 10-Qs and Ks from 2012Q4.[*]ftp://ftp.sec.gov/edgar/data/1001288/0001001288-12-000041.txt[*]ftp://ftp.sec.gov/edgar/data/1002037/0001193125-12-506687.txt[*]ftp://ftp.sec.gov/edgar/data/1002360/0001000096-12-000199.txtThe line items are standardized; however, there are many of them per document. For instance, one document will have a few \[code\]us-gaap:OperatingIncomeLoss\[/code\]es, and the only way I can tell that they denote which period they are reporting is with \[code\]contextRef\[/code\]. That's where things get complicated.I see no discernible pattern. Sometimes they're ascending then descending. They all have their own date formats. Some do multi-period grouping. Some don't.I've tried to find a standard on this. No go.Does anyone have any ideas?Many thanks!