Financial Instruments

6 Months Ended

Jun. 30, 2018

Cash and Cash Equivalents [Abstract]

Cash, Cash Equivalents and Restricted Cash

The following table summarizes the Company’s cash and cash equivalents and restricted cash (in thousands):



	June 30, 2018				December 31, 2017

	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value

Cash	$	58,492	$	58,492	$	101,356	$	101,356
Money market funds	91,380		91,380		79,256		79,256
	$	149,872	$	149,872	$	180,612	$	180,612
As reported
Cash and cash equivalents	$	91,596	$	91,596	$	103,828	$	103,828
Restricted cash	58,276		58,276		76,784		76,784
	$	149,872	$	149,872	$	180,612	$	180,612

As of June 30, 2018 and December 31, 2017, the Company had restricted cash of $58.3 million and $76.8 million, respectively, as follows (in thousands):



	June 30, 2018		December 31, 2017

Restricted cash related to PPA Entities	$	4,735	$	7,969
Restricted cash	21,125		36,418
Restricted cash, current	25,860		44,387
Restricted cash related to PPA Entities	27,604		26,748
Restricted cash	4,812		5,649
Restricted cash, non-current	32,416		32,397
Total restricted cash	$	58,276	$	76,784

Short-Term Investments

As of June 30, 2018 and December 31, 2017, the Company had short-term investments in U.S. Treasury Bills of $15.7 million and $26.8 million, respectively.

Derivative Instruments

The Company has derivative financial instruments related to natural gas forward contracts and interest rate swaps. See Note 7 - Derivative Instruments for a full description of the Company's derivative financial instruments.