What does high excess reserves mean for our economy, and how do they relate to Federal Reserve policies over the last decade?

I found this chart today and I found it quite shocking: http://ift.tt/1i1G7i9 It seems like the usual amount of excess reserves in financial institutions hovered around 1 Billion, but since the 2008, excess reserves have skyrocketed to incredible heights (currently $2.5 Trillion), increasing alongside QE each time it was in effect. What does this mean for our current economy? Do all of those reserves represent "real" wealth, as in wealth not created out of thin air by the Fed? Does it mean banks aren't lending as much as they have historically and are "hoarding" this capital for whatever reason? What effects does QE-money "hoarding" have on the current economy, does it mean there is less overal investment from banks? What's the reason behind such large excess reserves? Isn't QE supposed to encourage banks to lend more? I know the Fed spent about 4.5 Trillion total for QE 1,2, & 3, so this 2.5 Trillion represents about half of that total, right? Why would they hold on to so much cash?

link: http://ift.tt/1k4XYNv