4. Restricted Cash and Investments

Restricted cash and investments consisted of the following at March 31, 2019 and December 31, 2018 (in thousands):



	March 31, 2019		December 31, 2018
Restricted cash	$	169,529	$	139,390
Restricted investments	219,108		179,000
Total restricted cash and investments (1)	$	388,637	$	318,390

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(1)	There was an additional $23.7 million and $19.7 million of restricted cash included within “Prepaid expenses and other current assets” at March 31, 2019 and December 31, 2018, respectively.

At March 31, 2019 and December 31, 2018, our restricted cash consisted of deposits held by various banks to secure certain of our letters of credit and other deposits designated for the construction or operation of systems projects as well as the payment of amounts related to project specific debt financings. Restricted cash also included certain deposits held in custodial accounts to fund the estimated future costs of our solar module collection and recycling obligations.

At March 31, 2019 and December 31, 2018, our restricted investments consisted of long-term marketable securities that were also held in custodial accounts to fund the estimated future costs of collecting and recycling modules covered under our solar module collection and recycling program. As necessary, we fund any incremental amounts for our estimated collection and recycling obligations on an annual basis based on the estimated costs of collecting and recycling covered modules, estimated rates of return on our restricted investments, and an estimated solar module life of 25 years less amounts already funded in prior years. To ensure that amounts previously funded will be available in the future regardless of potential adverse changes in our financial condition (even in the case of our own insolvency), we have established a trust under which estimated funds are put into custodial accounts with an established and reputable bank, for which First Solar, Inc.; First Solar Malaysia Sdn. Bhd.; and First Solar Manufacturing GmbH are grantors. Trust funds may be disbursed for qualified module collection and recycling costs (including capital and facility related recycling costs), payments to customers for assuming collection and recycling obligations, and reimbursements of any overfunded amounts. Investments in the trust must meet certain investment quality criteria comparable to highly rated government or agency bonds.

During the three months ended March 31, 2019, we sold certain restricted investments for proceeds of $47.9 million and realized gains of $15.0 million on such sales as part of efforts to align the currencies of the investments with those of the corresponding collection and recycling liabilities and disburse $14.9 million of overfunded amounts. During the three months ended March 31, 2018, we sold certain restricted investments for proceeds of $101.6 million, realized gains of $19.5 million on such sales, and withdrew the funds from the trust as a reimbursement of overfunded amounts. See Note 8. “Fair Value Measurements” to our condensed consolidated financial statements for information about the fair value of our restricted investments.

The following tables summarize the unrealized gains and losses related to our restricted investments, by major security type, as of March 31, 2019 and December 31, 2018 (in thousands):



	As of March 31, 2019
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Foreign government obligations	$	119,161	$	5,505	$	—	$	124,666
U.S. government obligations	97,171		424		3,153		94,442
Total	$	216,332	$	5,929	$	3,153	$	219,108



	As of December 31, 2018
	Amortized Cost		Unrealized Gains		Unrealized Losses		Fair Value
Foreign government obligations	$	73,798	$	14,234	$	235	$	87,797
U.S. government obligations	97,223		416		6,436		91,203
Total	$	171,021	$	14,650	$	6,671	$	179,000

As of March 31, 2019, we identified six restricted investments totaling $91.3 million that had been in a loss position for a period of time greater than 12 months with unrealized losses of $3.2 million. As of December 31, 2018, we identified six restricted investments totaling $87.4 million that had been in a loss position for a period of time greater than 12 months with unrealized losses of $6.4 million. The unrealized losses were primarily due to increases in interest rates relative to rates at the time of purchase. Based on the underlying credit quality of the investments, we do not intend to sell these securities prior to the recovery of our cost basis. Therefore, we did not consider these investments to be other-than-temporarily impaired.

The following tables show unrealized losses and fair values for those restricted investments that were in an unrealized loss position as of March 31, 2019 and December 31, 2018, aggregated by major security type and the length of time the restricted investments have been in a continuous loss position (in thousands):



	As of March 31, 2019
	In Loss Position for Less Than 12 Months				In Loss Position for 12 Months or Greater				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
U.S. government obligations	$	—	$	—	$	91,266	$	3,153	$	91,266	$	3,153
Total	$	—	$	—	$	91,266	$	3,153	$	91,266	$	3,153



	As of December 31, 2018
	In Loss Position for Less Than 12 Months				In Loss Position for 12 Months or Greater				Total
	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
Foreign government obligations	$	41,335	$	235	$	—	$	—	$	41,335	$	235
U.S. government obligations	—		—		87,401		6,436		87,401		6,436
Total	$	41,335	$	235	$	87,401	$	6,436	$	128,736	$	6,671

As of March 31, 2019, the contractual maturities of our restricted investments were between 10 years and 20 years.