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Marketable Securities (Tables)
 6 Months Ended
Jul. 31, 2019
Investments Debt And Equity Securities [Abstract]  
Amortized Cost, Gross Unrealized Gains (Losses) and Fair Value of Available-For-Sale Securities The amortized cost, gross unrealized gains (losses) and fair value of available-for-sale securities by major security type and class of security as of July 31, 2019, January 31, 2019 and July 31, 2018 were as follows:

 

 

 

Amortized

 

 

Unrealized

 

 

Unrealized

 

 

Fair

 

 

 

Cost

 

 

Gains

 

 

(Losses)

 

 

Value

 

As of July 31, 2019

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Short-term Investments:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Corporate bonds

 

$

125,943

 

 

$

190

 

 

$

(31

)

 

$

126,102

 

Municipal and pre-refunded municipal bonds

 

 

42,023

 

 

 

40

 

 

 

(9

)

 

 

42,054

 

Certificates of deposit

 

 

1,745

 

 

 

—

 

 

 

—

 

 

 

1,745

 

Federal government agencies

 

 

1,495

 

 

 

2

 

 

 

—

 

 

 

1,497

 

 

 

 

171,206

 

 

 

232

 

 

 

(40

)

 

 

171,398

 

Long-term Investments:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Corporate bonds

 

 

49,385

 

 

 

174

 

 

 

(33

)

 

 

49,526

 

Municipal and pre-refunded municipal bonds

 

 

19,526

 

 

 

6

 

 

 

(50

)

 

 

19,482

 

Mutual funds, held in rabbi trust

 

 

7,826

 

 

 

56

 

 

 

(7

)

 

 

7,875

 

Certificates of deposit

 

 

1,847

 

 

 

—

 

 

 

—

 

 

 

1,847

 

Federal government agencies

 

 

126

 

 

 

1

 

 

 

—

 

 

 

127

 

 

 

 

78,710

 

 

 

237

 

 

 

(90

)

 

 

78,857

 

 

 

$

249,916

 

 

$

469

 

 

$

(130

)

 

$

250,255

 

As of January 31, 2019

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Short-term Investments:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Corporate bonds

 

$

227,287

 

 

$

24

 

 

$

(214

)

 

$

227,097

 

Municipal and pre-refunded municipal bonds

 

 

43,677

 

 

 

15

 

 

 

(18

)

 

 

43,674

 

Certificates of deposit

 

 

1,050

 

 

 

—

 

 

 

—

 

 

 

1,050

 

Federal government agencies

 

 

1,458

 

 

 

—

 

 

 

—

 

 

 

1,458

 

Commercial paper

 

 

2,979

 

 

 

—

 

 

 

—

 

 

 

2,979

 

Treasury bills

 

 

2,975

 

 

 

—

 

 

 

(1

)

 

 

2,974

 

 

 

 

279,426

 

 

 

39

 

 

 

(233

)

 

 

279,232

 

Long-term Investments:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Corporate bonds

 

 

34,265

 

 

 

34

 

 

 

(63

)

 

 

34,236

 

Municipal and pre-refunded municipal bonds

 

 

7,554

 

 

 

7

 

 

 

(3

)

 

 

7,558

 

Mutual funds, held in rabbi trust

 

 

6,301

 

 

 

450

 

 

 

—

 

 

 

6,751

 

Certificates of deposit

 

 

2,143

 

 

 

—

 

 

 

—

 

 

 

2,143

 

Federal government agencies

 

 

6,603

 

 

 

2

 

 

 

(1

)

 

 

6,604

 

 

 

 

56,866

 

 

 

493

 

 

 

(67

)

 

 

57,292

 

 

 

$

336,292

 

 

$

532

 

 

$

(300

)

 

$

336,524

 

 

 

Amortized

 

 

Unrealized

 

 

Unrealized

 

 

Fair

 

 

 

Cost

 

 

Gains

 

 

(Losses)

 

 

Value

 

As of July 31, 2018

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Short-term Investments:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Corporate bonds

 

$

150,648

 

 

$

—

 

 

$

(261

)

 

$

150,387

 

Municipal and pre-refunded municipal bonds

 

 

46,904

 

 

 

10

 

 

 

(43

)

 

 

46,871

 

Certificates of deposit

 

 

908

 

 

 

—

 

 

 

—

 

 

 

908

 

 

 

 

198,460

 

 

 

10

 

 

 

(304

)

 

 

198,166

 

Long-term Investments:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Corporate bonds

 

 

34,333

 

 

 

—

 

 

 

(213

)

 

 

34,120

 

Municipal and pre-refunded municipal bonds

 

 

2,130

 

 

 

1

 

 

 

(7

)

 

 

2,124

 

Mutual funds, held in rabbi trust

 

 

6,401

 

 

 

171

 

 

 

(1

)

 

 

6,571

 

Certificates of deposit

 

 

2,699

 

 

 

—

 

 

 

—

 

 

 

2,699

 

 

 

 

45,563

 

 

 

172

 

 

 

(221

)

 

 

45,514

 

 

 

$

244,023

 

 

$

182

 

 

$

(525

)

 

$

243,680