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Marketable Securities (Tables)
 9 Months Ended
Oct. 31, 2018
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 October 31, 2018, January 31, 2018 and October 31, 2017 were as follows:

 

 

 

Amortized

 

 

Unrealized

 

 

Unrealized

 

 

Fair

 

 

 

Cost

 

 

Gains

 

 

(Losses)

 

 

Value

 

As of October 31, 2018

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Short-term Investments:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Corporate bonds

 

$

200,910

 

 

$

—

 

 

$

(466

)

 

$

200,444

 

Municipal and pre-refunded municipal bonds

 

 

33,291

 

 

 

—

 

 

 

(59

)

 

 

33,232

 

Certificates of deposit

 

 

755

 

 

 

—

 

 

 

—

 

 

 

755

 

Commercial paper

 

 

2,960

 

 

 

—

 

 

 

—

 

 

 

2,960

 

 

 

 

237,916

 

 

 

—

 

 

 

(525

)

 

 

237,391

 

Long-term Investments:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Corporate bonds

 

 

24,793

 

 

 

—

 

 

 

(175

)

 

 

24,618

 

Municipal and pre-refunded municipal bonds

 

 

2,573

 

 

 

—

 

 

 

(7

)

 

 

2,566

 

Mutual funds, held in rabbi trust

 

 

6,932

 

 

 

—

 

 

 

(473

)

 

 

6,459

 

Certificates of deposit

 

 

2,390

 

 

 

—

 

 

 

—

 

 

 

2,390

 

 

 

 

36,688

 

 

 

—

 

 

 

(655

)

 

 

36,033

 

 

 

$

274,604

 

 

$

—

 

 

$

(1,180

)

 

$

273,424

 

As of January 31, 2018

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Short-term Investments:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Corporate bonds

 

$

111,612

 

 

$

—

 

 

$

(184

)

 

$

111,428

 

Municipal and pre-refunded municipal bonds

 

 

52,474

 

 

 

11

 

 

 

(39

)

 

 

52,446

 

Certificates of deposit

 

 

1,251

 

 

 

—

 

 

 

—

 

 

 

1,251

 

 

 

 

165,337

 

 

 

11

 

 

 

(223

)

 

 

165,125

 

Long-term Investments:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Corporate bonds

 

 

39,853

 

 

 

—

 

 

 

(228

)

 

 

39,625

 

Municipal and pre-refunded municipal bonds

 

 

9,873

 

 

 

8

 

 

 

(24

)

 

 

9,857

 

Mutual funds, held in rabbi trust

 

 

5,973

 

 

 

274

 

 

 

(10

)

 

 

6,237

 

Certificates of deposit

 

 

2,969

 

 

 

—

 

 

 

—

 

 

 

2,969

 

 

 

 

58,668

 

 

 

282

 

 

 

(262

)

 

 

58,688

 

 

 

$

224,005

 

 

$

293

 

 

$

(485

)

 

$

223,813

 

As of October 31, 2017

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Short-term Investments:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Corporate bonds

 

$

67,275

 

 

$

2

 

 

$

(71

)

 

$

67,206

 

Municipal and pre-refunded municipal bonds

 

 

24,676

 

 

 

4

 

 

 

(14

)

 

 

24,666

 

Certificates of deposit

 

 

1,356

 

 

 

—

 

 

 

—

 

 

 

1,356

 

 

 

 

93,307

 

 

 

6

 

 

 

(85

)

 

 

93,228

 

Long-term Investments:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Corporate bonds

 

 

30,051

 

 

 

2

 

 

 

(87

)

 

 

29,966

 

Municipal and pre-refunded municipal bonds

 

 

1,362

 

 

 

—

 

 

 

(2

)

 

 

1,360

 

Mutual funds, held in rabbi trust

 

 

5,639

 

 

 

109

 

 

 

(2

)

 

 

5,746

 

Certificates of deposit

 

 

4,182

 

 

 

—

 

 

 

—

 

 

 

4,182

 

 

 

 

41,234

 

 

 

111

 

 

 

(91

)

 

 

41,254

 

 

 

$

134,541

 

 

$

117

 

 

$

(176

)

 

$

134,482