Cash, Cash Equivalents and Investments (Tables)
 3 Months Ended
Mar. 31, 2018
Cash and Cash Equivalents [Abstract]  
Summary of Cash, Cash Equivalents and Investments
Our total cash, cash equivalents and investments are summarized below:
 
March 31, 2018
December 31, 2017
(in millions)
Cash and cash equivalents
Available for sale marketable securities
Certificate
of
deposits
Total
Cash and cash equivalents
Available for sale marketable securities
Certificate
of
deposits
Total
Cash and cash equivalents
$
330

$
—

$
—

$
330

$
336

$
—

$
—

$
336

Restricted cash, cash equivalents and investments
 
 
 
 
 
 
 
 
Insurance carriers security deposits
15

—

—

15

15

—

—

15

Payroll funds collected
523

—

—

523

1,095

—

—

1,095

Collateral for health benefits claims
71

—

—

71

69

—

—

69

Collateral for workers' compensation claims
87

1

—

88

98

1

—

99

Collateral to secure standby letter of credit
—

—

2

2

—

—

2

2

Total restricted cash, cash equivalents and investments
696

1

2

699

1,277

1

2

1,280

Restricted cash, cash equivalents and investments, noncurrent
 
 
 
 
 
 
 
 
Collateral for workers' compensation claims
159

23

—

182

125

37

—

162

Total
$
1,185

$
24

$
2

$
1,211

$
1,738

$
38

$
2

$
1,778
Amortized Cost, Gross Unrealized Gains and Losses, Fair Values and Related Maturities of Securities Available for Sale
The amortized cost, gross unrealized gains, gross unrealized losses, fair values, and related maturities of securities available for sale as of March 31, 2018 and December 31, 2017 are presented below:
(in millions)
Maturity
(in years)
Amortized Cost
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value
March 31, 2018
 
 
 
 
 
U.S. treasuries
1-5 years
$
23

$
—

$
—

$
23

Exchange traded fund
N/A
1

—

—

1

Total
 
$
24

$
—

$
—

$
24

 
 
 
 
 
 
December 31, 2017
 
 
 
 
 
U.S. treasuries
1-5 years
$
37

$
—

$
—

$
37

Exchange traded fund
N/A
1

—

—

1

Total
 
$
38

$
—

$
—

$
38