directors. Farmer Mac generally requires financial institutions to own a requisite amount of common stock, based on the size and type of institution, to participate in the Farm & Ranch line of business. As a result of these requirements, Farmer Mac conducts business with related parties in the normal course of Farmer Mac's business. All related party transactions were conducted with terms and conditions comparable to those available to any other participant in Farmer Mac's lines of business not related to Farmer Mac.

Farmer Mac considers Zions Bancorporation, National Association and its affiliates ("Zions") a related party due to the ownership by Zions of approximately 31.2% of Farmer Mac's Class A voting common stock. The following transactions occurred between Farmer Mac and Zions during 2019, 2018, and 2017:


	For the Years Ended December 31,
	2019		2018		2017
	(in thousands)
Unpaid Principal Balance:
Purchases:
Loans	$	129,040	$	114,719	$	126,449
USDA Securities	8,875		19,120		20,368
Sales of Farmer Mac Guaranteed Securities	163,134		68,721		128,924

The purchases of loans from Zions under the Farm & Ranch line of business represented approximately 9.5%, 11.9%, and 11.2% of Farm & Ranch loan purchases for the years ended December 31, 2019, 2018, and 2017, respectively, and 7.6%, 8.2% and 7.5%, respectively, of total new Farm & Ranch business volume. The purchases of USDA Securities from Zions under the USDA Guarantees line of business represented approximately 2.1%, 4.2%, and 3.8% of purchases in that line of business for the years ended December 31, 2019, 2018, and 2017, respectively. Outstanding Farm & Ranch loans, USDA Securities, and AgVantage securities purchased from Zions represented 4.5% and 4.7%, respectively, of Farmer Mac's outstanding business volume as of December 31, 2019 and 2018.

Zions retained servicing fees of $12.2 million, $11.6 million, and $11.5 million in 2019, 2018, and 2017, respectively, for its work as a Farmer Mac servicer.

Farmer Mac considers the National Rural Utilities Cooperative Financial Corporation ("CFC") a related party because of its ownership of approximately 7.9% of Farmer Mac's Class A voting common stock and because a member of Farmer Mac's board of directors has an affiliation with that entity. The following transactions occurred between Farmer Mac and CFC during 2019, 2018, and 2017:


Farmer Mac Loan Purchases and Guarantees
	For the Years Ended December 31,
	2019		2018		2017
	(in thousands)
Unpaid Principal Balance:
Loans	$	85,000	$	11,645	$	137,341
On-balance sheet AgVantage Securities	575,000		675,000		350,000
Off-balance sheet revolving floating rate AgVantage facility	—		300,000		—

Total purchases and guarantees	$	660,000	$	986,645	$	487,341

The transactions with CFC represented 9.8% of Farmer Mac's loan purchase volume under the Rural Utilities line of business for 2019, compared to 100% of Farmer Mac's loan purchase volume for both 2018 and 2017. These transactions represented 25.5%, 29.5%, and 14.7% of AgVantage securities volume under the Institutional Credit line of business for 2019, 2018, and 2017, respectively, and represented 12.5%, 19.1%, and 10.3% of total purchases, guarantees, and LTSPCs for 2019, 2018, and 2017, respectively. Of Farmer Mac's total outstanding business volume as of December 31, 2019 and 2018, Rural Utilities loans, loans under LTSPCs, and AgVantage securities issued by CFC represented 21.2% and 23.6%, respectively.

Farmer Mac had interest receivable of $9.2 million and $9.4 million as of December 31, 2019 and 2018, respectively, and earned interest income of $97.3 million, $76.8 million, and $43.9 million during 2019, 2018, and 2017, respectively, related to its AgVantage transactions with CFC.

As of both December 31, 2019 and 2018, Farmer Mac had $0.1 million of commitment fees receivable from CFC and earned commitment fees of $1.7 million, $1.9 million, and $2.2 million, respectively for 2019, 2018, and 2017.

CFC retained servicing fees of $3.2 million, $3.6 million and $3.5 million in 2019, 2018, and 2017, respectively, for its work as a Farmer Mac central servicer.

Farmer Mac has a related party relationship with CoBank because CoBank is a major holder (32.6%) of Farmer Mac Class B voting common stock and because a member of Farmer Mac's board of directors has an affiliation with that entity.

Farmer Mac entered into $776.4 million of loan purchases from CoBank, under the Rural Utilities line of business in 2019. The transactions with CoBank represented 89.1% of Farmer Mac's volume of loan purchases transactions under the Rural Utilities line of business for 2019. During 2018 and 2017, Farmer Mac did not do any business with CoBank through any of its lines of business.

CoBank retained servicing fees of $1.2 million during 2019 for its work as a Farmer Mac central servicer. During 2018 and 2017, CoBank was not a Farmer Mac central servicer.

Farmer Mac has a related party relationship with AgFirst Farm Credit Bank ("AgFirst") resulting from AgFirst being a holder of approximately 16.8% of Farmer Mac's Class B voting common stock.

AgFirst entered into $26.7 million, $26.6 million and $40.0 million of LTSPC transactions in 2019, 2018, and 2017, respectively, and the aggregate balance of LTSPCs outstanding as of December 31, 2019 and 2018 was $332.4 million and $340.5 million, respectively. Farmer Mac received from AgFirst $1.2 million, $1.2 million, and $1.1 million in commitment fees in 2019, 2018, and 2017, respectively, and had $0.1 million of commitment fees receivable as of both December 31, 2019 and 2018.

AgFirst owns certain securities backed by rural housing loans. Farmer Mac guarantees the last ten percent of losses (based on the original principal balance at the time of pooling) from each loan in the pool backing those securities. As of December 31, 2019 and 2018, the outstanding balance of those securities owned by AgFirst was $7.0 million and $8.6 million, respectively. Farmer Mac received guarantee fees of $29,000, $33,000, and $38,000 in 2019, 2018, and 2017, respectively, on those securities.

Farmer Mac has a related party relationship with Farm Credit Bank of Texas resulting from the bank being a holder of approximately 7.7% of Farmer Mac Class B voting common stock and because a member of Farmer Mac's board of directors has an affiliation with that entity. Farmer Mac received from Farm Credit Bank of Texas commitment fees of $1.1 million, $1.0 million, and $1.0 million in 2019, 2018, and 2017, respectively. The aggregate amount of LTSPCs outstanding with Farm Credit Bank of Texas as of December 31, 2019 and 2018 was $270.3 million and $226.5 million, respectively. In 2019, 2018, and 2017, Farm Credit Bank of Texas retained $0.1 million, $0.2 million, and $0.2 million, respectively, in servicing fees for its work as a Farmer Mac central servicer.

The following institutions had a related party relationship with Farmer Mac because a member of Farmer Mac's board of directors is affiliated with each of those entities.

Farmer Mac purchased $51.4 million, $39.5 million, and $28.5 million in loans from First Dakota National Bank in 2019, 2018, and 2017, respectively. Farmer Mac entered into $3.2 million, $3.0 million, and $0.4 million of new USDA Securities in 2019, 2018, and 2017, respectively, with First Dakota National Bank. In addition, Farmer Mac entered into $3.6 million, $0.0 million, and $0.0 million of new LTSPCs in 2019, 2018, and 2017, respectively, with First Dakota National Bank. First Dakota National Bank retained servicing fees of $1.2 million, $1.4 million, and $1.2 million in 2019, 2018, and 2017, respectively, for its work as a Farmer Mac servicer.