It is a game of inches, but there is definitely movement!
Allstate (not to pick on them, but I needed to pick an example) created the extension concept all:CashPeriodIncreaseDecrease in this filing (screen shot below) and used it to express net cash flow per their cash flow statement:
Allstate has subsequently changed this and now they use the US GAAP Taxonomy concept us-gaap:CashPeriodIncreaseDecrease (this screen shot) on their cash flow statement:
This is a small move, but I am seeing lots and lots of these sorts of these small, positive movements in SEC XBRL financial filings. There is a ways to go, but the momentum is building.