(1) Includes $11 million and $34 million of margin deposits held by us posted by our counterparties at December 31, 2012, and 2011, respectively.
(2) Includes availability under our CDHI letter of credit facility. On January 10, 2012, we increased the CDHI letter of credit facility to $300 million and extended the maturity date to January 2, 2016. As a result of the completion of the sale of Riverside Energy Center, LLC, a wholly owned subsidiary of CDHI, on December 31, 2012, we are required to cash collateralize letters of credit issued in excess of $225 million until replacement collateral is contributed to the CDHI collateral package, which we are in the process of arranging. At December 31, 2012, we had $28 million of cash collateral posted in support of outstanding letters of credit under our CDHI letter of credit facility. We do not believe that this change will have a material impact on our liquidity.
Liquidity increased to approximately $2.3 billion as of December 31, 2012, up from approximately $2.0 billion at December 31, 2011.
Cash flows from operating activities in 2012 resulted in net inflows of $653 million compared to $775 million in 2011. The decrease in cash provided by operating activities was primarily due to an increase in cash paid for interest due to timing of interest payments on our debt and an increase in working capital driven by higher margin requirements.Cash flows used in investing activities decreased to $470 million in 2012 compared to $836 million in 2011, driven largely by higher proceeds from the sales of our Broad River and Riverside Energy Centers, partially offset by the purchase of our Bosque Energy Center. Cash flows used in financing activities were $151 million in 2012, driven largely by $463 million in share repurchases in 2012, partially offset by net proceeds from borrowing on our project debt facilities and our 2012 refinancing activities, as further described below.