Debt of Consolidated Variable Interest Entities
As of June 30, 2016 and December 31, 2015, debt of consolidated VIEs, at fair value, was $528 million and $595 million, respectively, and had a weighted average interest rate of LIBOR plus 36 and 34 basis points, respectively, and a principal balance of $523 million and $587 million, respectively. The actual maturities of our debt of consolidated VIEs are generally shorter than the stated contractual maturities. The actual maturities are affected by the contractual lives of the underlying agency MBS securitizing the debt of our consolidated VIEs and periodic principal prepayments of such underlying securities. The estimated weighted average life of the debt of our consolidated VIEs as of June 30, 2016 and December 31, 2015 was 4.8 and 4.9 years, respectively.
Note 6. Derivative and Other Hedging Instruments
In connection with our risk management strategy, we hedge a portion of our interest rate risk by entering into derivative and other hedging instrument contracts. The principal instruments that we use are interest rate swaps and interest rate swaptions and U.S. Treasury securities and U.S. Treasury futures contracts, primarily through short sales. We may also utilize TBA securities, purchase or write put or call options on TBA securities or invest in mortgage and other types of derivatives, such as interest and principal-only securities. We also enter into TBA contracts as a means of investing in and financing agency securities (thereby increasing our "at risk" leverage) or as a means of disposing of or reducing our exposure to agency securities (thereby reducing our "at risk" leverage). Our risk management strategy attempts to manage the overall risk of the portfolio, reduce fluctuations in our net book value and generate additional income distributable to stockholders. For additional information regarding our derivative instruments and our overall risk management strategy, please refer to the discussion of derivative and other hedging instruments in Note 3.
Prior to September 30, 2011, our interest rate swaps were typically designated as cash flow hedges under ASC 815; however, as of September 30, 2011, we elected to discontinue hedge accounting for our interest rate swaps in order to increase our funding flexibility. For the three and six months ended June 30, 2016, we reclassified $12 million and $31 million, respectively, and for the three and six months ended June 30, 2015 $26 million and $55 million, respectively, of net deferred losses from accumulated OCI into interest expense related to our de-designated interest rate swaps and recognized an equal, but offsetting, amount in other comprehensive income. Our total net periodic interest costs on our swap portfolio were $81 million and $189 million for the three and six months ended June 30, 2016, respectively, and $125 million and $238 million for the three and six months ended June 30, 2015, respectively. The difference between our total net periodic interest costs on our swap portfolio and the amount recorded in interest expense related to our de-designated hedges is reported in gain (loss) on derivative instruments and other securities, net in our accompanying consolidated statements of comprehensive income (totaling $69 million and $158 million for the three and six months ended June 30, 2016, respectively, and $99 million and $183 million for the three and six months ended June 30, 2015, respectively). As of June 30, 2016, the remaining net deferred loss in accumulated OCI related to de-designated interest rate swaps was $8 million.