Financial Instruments

9 Months Ended

Sep. 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):



	September 30, 2018				December 31, 2017
	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value

Cash	$	84,151	$	84,151	$	101,356	$	101,356
Money market funds	360,075		360,075		79,256		79,256
	$	444,226	$	444,226	$	180,612	$	180,612
As reported
Cash and cash equivalents	$	395,516	$	395,516	$	103,828	$	103,828
Restricted cash	48,710		48,710		76,784		76,784
	$	444,226	$	444,226	$	180,612	$	180,612

As of September 30, 2018 and December 31, 2017, the Company had restricted cash of $48.7 million and $76.8 million, respectively, as follows (in thousands):



	September 30, 2018		December 31, 2017

Restricted cash related to PPA Entities	$	3,252	$	7,969
Restricted cash	14,679		36,418
Restricted cash, current	17,931		44,387
Restricted cash related to PPA Entities	27,778		26,748
Restricted cash	3,001		5,649
Restricted cash, non-current	30,779		32,397
Total restricted cash	$	48,710	$	76,784

Short-Term Investments

As of September 30, 2018 and December 31, 2017, the Company had short-term investments in U.S. Treasury Bills of $4.5 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 Financial Instruments for a full description of the Company's derivative financial instruments.