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Marketable Securities (Tables)
 3 Months Ended
Apr. 30, 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 April 30, 2018, January 31, 2018 and April 30, 2017 were as follows:

 

 

 

Amortized

 

 

Unrealized

 

 

Unrealized

 

 

Fair

 

 

 

Cost

 

 

Gains

 

 

(Losses)

 

 

Value

 

As of April 30, 2018

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Short-term Investments:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Corporate bonds

 

$

110,657

 

 

$

—

 

 

$

(294

)

 

$

110,363

 

Municipal and pre-refunded municipal bonds

 

 

54,659

 

 

 

—

 

 

 

(47

)

 

 

54,612

 

Certificates of deposit

 

 

1,392

 

 

 

—

 

 

 

—

 

 

 

1,392

 

 

 

 

166,708

 

 

 

—

 

 

 

(341

)

 

 

166,367

 

Long-term Investments:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Corporate bonds

 

 

18,137

 

 

 

—

 

 

 

(212

)

 

 

17,925

 

Municipal and pre-refunded municipal bonds

 

 

7,873

 

 

 

—

 

 

 

(30

)

 

 

7,843

 

Mutual funds, held in rabbi trust

 

 

6,453

 

 

 

33

 

 

 

(3

)

 

 

6,483

 

Certificates of deposit

 

 

2,828

 

 

 

—

 

 

 

—

 

 

 

2,828

 

 

 

 

35,291

 

 

 

33

 

 

 

(245

)

 

 

35,079

 

 

 

$

201,999

 

 

$

33

 

 

$

(586

)

 

$

201,446

 

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 April 30, 2017

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Short-term Investments:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Corporate bonds

 

$

77,313

 

 

$

4

 

 

$

(58

)

 

$

77,259

 

Municipal and pre-refunded municipal bonds

 

 

40,788

 

 

 

24

 

 

 

(3

)

 

 

40,809

 

Certificates of deposit

 

 

425

 

 

 

—

 

 

 

—

 

 

 

425

 

 

 

 

118,526

 

 

 

28

 

 

 

(61

)

 

 

118,493

 

Long-term Investments:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Corporate bonds

 

 

27,586

 

 

 

3

 

 

 

(36

)

 

 

27,553

 

Municipal and pre-refunded municipal bonds

 

 

4,758

 

 

 

17

 

 

 

—

 

 

 

4,775

 

Mutual funds, held in rabbi trust

 

 

5,011

 

 

 

62

 

 

 

(1

)

 

 

5,072

 

Certificates of deposit

 

 

1,051

 

 

 

—

 

 

 

—

 

 

 

1,051

 

 

 

 

38,406

 

 

 

82

 

 

 

(37

)

 

 

38,451

 

 

 

$

156,932

 

 

$

110

 

 

$

(98

)

 

$

156,944