Supplemental Financial Statement Information (Tables)

6 Months Ended

Jun. 30, 2019

Balance Sheet Components Disclosure [Abstract]

Summary of Cash Equivalents and Short-Term Investments

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):

	June 30, 2019
	Cost or Amortized		Unrealized					Estimated Fair
	Cost		Gains		Losses			Value
Unrestricted Balances(1)
Money market funds	$	67,232	$	—	$	—		$	67,232
Term deposit		105,000		—		—			105,000
Certificates of deposit		1,486,173		2,284		(1	)		1,488,456
Commercial paper		1,025,517		332		(84	)		1,025,765
Corporate bonds		284,195		482		—			284,677
Total unrestricted cash equivalents and short-term investments		2,968,117		3,098		(85	)		2,971,130
Restricted Balances(2)(3)
Money market funds		1,438		—		—			1,438
Certificates of deposit		433,859		608		(4	)		434,463
Commercial paper		734,240		211		(71	)		734,380
Corporate bonds		62,450		82		(1	)		62,531
Total restricted cash equivalents and investments		1,231,987		901		(76	)		1,232,812
Total unrestricted and restricted cash equivalents and investments	$	4,200,104	$	3,999	$	(161	)	$	4,203,942

(1) Included in cash and cash equivalents and short-term investments in the Company’s condensed consolidated balance sheet as of June 30, 2019 in addition to $339.2 million of cash.

(2) Included in restricted cash and cash equivalents and restricted investments in the Company’s condensed consolidated balance sheet as of June 30, 2019 in addition to $57.6 million of restricted cash.

(3) Included in prepaid expenses and other current assets in the Company’s condensed consolidated balance sheet as of June 30, 2019 is $2.1 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.

Summary of Rollforward of the Insurance Reserve

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

	Six Months Ended June 30,
	2019			2018
Beginning balance	$	810,273		$	376,538
Losses paid		(205,629	)		(95,881	)
Change in estimates for prior periods		137,840			3,392
Reserves for current period		464,896			290,868
Ending balance	$	1,207,380		$	574,917