premiums and losses ceded under our internal quota share arrangement described below, which are captured in our Excess and Surplus Lines and Specialty Admitted Insurance segments. Typically, we structure our reinsurance contracts as quota share arrangements, with loss mitigating features, such as commissions that adjust based on underwriting results. We frequently include risk mitigating features in our excess working layer treaties, which allows the ceding company to capture a greater percentage of the profits should the business prove more profitable than expected, or alternatively provides us with additional premiums should the business incur higher than expected losses. We believe these structures allow us to participate in the risk side-by-side with the ceding company and best align our interests with the interests of our cedents. Treaties with loss mitigation features including sliding scale ceding commissions represented 85.6% of the gross premiums written by our Casualty Reinsurance segment during 2016. We typically do not assume large individual risks in our Casualty Reinsurance segment, nor do we write property catastrophe reinsurance. Two of the three largest unaffiliated accounts written by JRG Re in 2016 were assumed from E&S carriers. The Casualty Reinsurance segment distributes through traditional reinsurance brokers. The Casualty Reinsurance segment produced 25.0% of our gross written premiums and 33.2% of our net written premiums for the year ended December 31, 2016.
During 2016, 2015 and 2014, we had a number of our bank loans to oil and gas companies in the energy sector. The market value of these loans declined significantly in response to declining energy prices. We determined that a total credit allowance of  $545,000 on one loan at December 31, 2016 and $3.9 million
The net premium retention for the Company decreased from 82.3% to 75.6% for the years ended December 31, 2015 and 2016, respectively. The decrease in retention is due primarily to the Specialty Admitted Insurance segment, which saw a decline in its net premium retention from 49.4% for the year ended December 31, 2015 to 30.6% for the year ended December 31, 2016. Fronting and program business generally has much lower net premium retention than our workers’ compensation business which we write on an admitted basis. For the year ended December 31, 2016, the net retention on the segment’s fronting and program business was 14.0%, while the net retention on the workers’ compensation business was 90.3%. This compares to net retention on the segment’s fronting and program business of 22.6% and net retention of the workers’ compensation business of 90.4% for year ended December 31, 2015. The net retention for the Excess and Surplus Lines segment increased from 80.2% in 2015 to 84.3% in 2016. The net retention for the Casualty Reinsurance segment for 2016 and 2015 includes adjustments of both gross and net written premiums from the prior year that caused this segment’s net premium retention to slightly exceed 100% for both years.
Loss Ratio. The loss ratio for the year ended December 31, 2016 of 65.3% included $4.2 million, or 2.6 percentage points, of adverse reserve development in our loss estimates for prior accident years. The loss ratio for the year ended December 31, 2015 of 68.6% included $12.6 million, or 7.1 percentage points, of adverse reserve development in our loss estimates for prior accident years.
The Company’s bank loan portfolio includes loans to oil and gas companies in the energy sector. The market values of these loans were impacted by declining energy prices in 2015. At December 31, 2015, the Company’s oil and gas exposure in the bank loan portfolio was in eight loans with a carrying value of $15.8 million and an unrealized loss of  $4.1 million. Management concluded that two of these loans were impaired as of December 31, 2015, and accordingly, an allowance for credit losses of  $3.9 million was established on the loans. After recording this impairment, the loans had a carrying value of $1.7 million at December 31, 2015 and unpaid principal of $5.8 million. At December 31, 2016, the Company’s oil and gas exposure was in four bank loans and with a total carrying value of  $9.8 million and an unrealized loss of $1.3 million. Management concluded that one of these loans was impaired with a carrying value of  $1.6 million, unpaid principal of  $2.2 million and an allowance for credit losses of  $545,000. All of the other loans are current at December 31, 2016.
The Company recorded $597,000 of amortization of intangibles for each of the years ended December 31, 2016 and 2015, respectively.
The Company completed its impairment tests and fair value analyses for goodwill and other intangible assets during the fourth quarter. No impairment was present for the years ended December 31, 2016 or 2015.
The $191.7 million of bank loan participations are classified as held-for-investment and reported at amortized cost, net of an allowance for credit losses of   $4.3 million. The allowance for credit losses at December 31, 2015 was primarily related to two Puerto Rico loans and two energy sector loans (the allowance for credit losses was $752,000 at December 31, 2014 and was related to two Puerto Rico loans). Changes in this credit allowance are included in realized gains or losses. At December 31, 2015 and 2014, the fair market value of these securities was $180.1 million and $231.3 million, respectively.
At December 31, 2015, our portfolio of available-for-sale fixed maturity securities contained corporate fixed maturity securities with a fair value of  $363.2 million. A summary of these securities by industry segment is shown below as of December 31, 2015:
At December 31, 2015, the Company had no investments in securitizations of alternative-A mortgages, sub-prime mortgages, or collateralized debt obligations.
The following table reconciles the underwriting profit (loss) by individual segment and of the Company as a whole to consolidated income before U.S. federal income taxes for the years ended December 31, 2016, 2015 and 2014.
Underwriting profit includes fee income of $14.2 million, $5.0 million, and $1.8 million for the years ended December 31, 2016, 2015, and 2014, respectively.