The cost of deposits declined during the quarter to 0.49% from 0.58% for the third quarter due to continued growth in low-cost core deposits, as well as a decline in average yield on time deposits primarily resulting from the Southern Community acquisition.
Net Interest Income and Net Interest Margin
Net interest income for the fourth quarter of 2012 increased by approximately $5.7 million, or 9.4%, to $66.0 million, from $60.3 million for the third quarter of 2012 and increased $2.4 million, or 3.8%, from the fourth quarter of 2011. The main driver of the increase in net interest income for the quarter was the addition of Southern Community.
Net interest margin for the quarter was 4.11%, a reduction of 34 basis points that was largely driven by the acquisition of Southern Community and the high level of low yielding securities held by that bank at the point of merger. These effects, combined, equated to 23 basis points of the decline. New originations, which were booked at an average yield of 4.27%, normal reinvestment activity and changes in funding cost caused an additional decline of 11 basis points, as compared to the 15 basis point contraction we experienced in the third quarter.
Non-interest income decreased $5.1 million to $15.3 million for the fourth quarter of 2012 from $20.4 million for the third quarter and decreased $0.7 million from $16.0 million for the fourth quarter of 2011. The decrease in the fourth quarter was driven by a $4.9 million decline in investment securities gains, a quarter over quarter change in FDIC indemnification asset accretion of $0.5 million and the absence of $3.5 million of legal and insurance settlement gains recognized in the third quarter. These declines were offset by a $2.3 million increase in service charges on deposits income, debit card income and fees on mortgage loans sold, coupled with the addition of Southern Community.