The following tables summarize the cost or amortized cost, gross unrealized gain, gross unrealized loss and fair value of the Company’s cash equivalents and short-term investments as of the dates indicated (in thousands):

	March 31, 2019
	Cost or Amortized		Unrealized					Estimated Fair
	Cost		Gains		Losses			Value
Unrestricted Balances (1)
Money market funds	$	1,406	$	—	$	—		$	1,406
Certificates of deposit		168,700		203		—			168,903
Commercial paper		441,803		190		(32	)		441,961
Corporate bonds		94,415		93		(1	)		94,507
Total unrestricted cash equivalents and short-term investments		706,324		486		(33	)		706,777
Restricted Balances (2)(3)
Money market funds		2,822		—		—			2,822
Certificates of deposit		348,007		364		(2	)		348,369
Commercial paper		696,251		176		(90	)		696,337
Corporate bonds		62,204		58		(8	)		62,254
Total restricted cash equivalents and investments		1,109,284		598		(100	)		1,109,782
Total unrestricted and restricted cash equivalents and investments	$	1,815,608	$	1,084	$	(133	)	$	1,816,559

(1)	Included in cash and cash equivalents and short-term investments in the Company’s condensed consolidated balance sheet as of March 31, 2019 in addition to $328.1 million of cash.

(2)	Included in restricted cash and cash equivalents and restricted investments in the Company’s condensed consolidated balance sheet as of March 31, 2019 in addition to $58.0 million of restricted cash.

(3)	Included in prepaid expenses and other current assets in the Company’s condensed consolidated balance sheet as of March 31, 2019 is $1.9 million of restricted cash.

	December 31, 2018
	Cost or Amortized		Unrealized					Estimated Fair
	Cost		Gains		Losses			Value
Unrestricted Balances (1)
Money market funds	$	38,528	$	—	$	—		$	38,528
Certificates of deposit		497,748		19		(213	)		497,554
Commercial paper		1,135,092		38		(409	)		1,134,721
Corporate bonds		119,043		19		(23	)		119,039
Total unrestricted cash equivalents and short-term investments		1,790,411		76		(645	)		1,789,842
Restricted Balances (2)(3)
Money market funds		4,620		—		—			4,620
Certificates of deposit		307,650		41		(87	)		307,604
Commercial paper		624,719		17		(227	)		624,509
Corporate bonds		65,616		6		(36	)		65,586
Total restricted cash equivalents and investments		1,002,605		64		(350	)		1,002,319
Total unrestricted and restricted cash equivalents and investments	$	2,793,016	$	140	$	(995	)	$	2,792,161

(1)	Included in cash and cash equivalents and short-term investments in the Company’s condensed consolidated balance sheet as of December 31, 2018 in addition to $248.0 million of cash.

(2)	Included in restricted cash and cash equivalents and restricted investments in the Company’s condensed consolidated balance sheet as of December 31, 2018 in addition to $50.2 million of restricted cash.

(3)	Included in prepaid expenses and other current assets in the Company’s condensed consolidated balance sheet as of December 31, 2018 is $1.4 million of restricted cash.

The Company’s short-term investments are classified as available-for-sale. Available-for-sale investments are reported at fair value, with unrealized gains and losses, included as a separate component of stockholders’ deficit within accumulated other comprehensive income.

The weighted-average remaining maturity of the Company’s investment portfolio was less than one year as of the periods presented. No individual security incurred continuous unrealized losses for greater than 12 months.

The following table provides a rollforward of the insurance reserve for the periods presented (in thousands):