Internet Initiative Japan (IIJIY) 20-F 16 Jul 14 2014 FY Annual report (foreign) Financial data

Document_And_Entity_Informatio

Document And Entity Information	12 Months Ended
	Mar. 31, 2014
Document and Entity Information [Abstract]	'
Entity Registrant Name	'INTERNET INITIATIVE JAPAN INC
Document Type	'20-F
Current Fiscal Year End Date	'--03-31
Entity Common Stock, Shares Outstanding	46,697,800
Amendment Flag	'false
Entity Central Index Key	'0001090633
Entity Current Reporting Status	'Yes
Entity Voluntary Filers	'No
Entity Filer Category	'Large Accelerated Filer
Entity Well-known Seasoned Issuer	'No
Document Period End Date	31-Mar-14
Document Fiscal Year Focus	'2014
Document Fiscal Period Focus	'FY

Consolidated_Balance_Sheets

Consolidated Balance Sheets	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013
In Thousands, unless otherwise specified	USD ($)	JPY (¥)	JPY (¥)
CURRENT ASSETS:	'	'	'
Cash and cash equivalents	$217,723	¥ 22,421,100	¥ 12,258,872
Accounts receivable, net of allowance for doubtful accounts of ¥93,934 thousand and ¥53,871 thousand ($523 thousand) at March 31, 2013 and 2014, respectively (Notes 5, 6 and 22)	186,582	19,214,248	18,764,703
Inventories (Note 3)	16,219	1,670,258	1,301,684
Prepaid expenses	30,377	3,128,290	2,492,164
Deferred tax assets―current (Note 12)	13,527	1,392,971	1,046,828
Guarantee deposits―current (Note 9)	14,199	1,462,223	1,200
Other current assets, net of allowance for doubtful accounts of ¥10,732 thousand and ¥720 thousand ($7 thousand) at March 31, 2013 and 2014, respectively (Notes 5 and 9)	23,416	2,411,376	1,575,518
Total current assets	502,043	51,700,466	37,440,969
INVESTMENTS IN EQUITY METHOD INVESTEES (Note 6)	20,253	2,085,689	1,681,723
OTHER INVESTMENTS (Notes 4, 17, 18 and 19)	61,719	6,355,817	3,771,262
PROPERTY AND EQUIPMENT—Net (Notes 7 and 9)	261,910	26,971,485	23,025,755
GOODWILL (Note 8)	57,972	5,969,951	5,969,951
OTHER INTANGIBLE ASSETS—Net (Note 8)	42,134	4,338,944	4,791,431
GUARANTEE DEPOSITS (Note 9)	12,280	1,264,535	2,051,449
DEFERRED TAX ASSETS―Noncurrent (Note 12)	6,184	636,807	163,773
NET INVESTMENT IN SALES-TYPE LEASES―Noncurrent (Note 9)	7,310	752,774	898,040
PREPAID EXPENSES―Noncurrent	25,569	2,633,154	2,201,108
OTHER ASSETS, net of allowance for doubtful accounts and loans of ¥71,727 thousand and ¥62,800 thousand ($610 thousand) at March 31, 2013 and 2014, respectively (Notes 5, 6 and 18)	11,235	1,156,953	115,805
TOTAL	1,008,609	103,866,575	82,111,266
CURRENT LIABILITIES:	'	'	'
Short-term borrowings (Note 11)	91,280	9,400,000	9,400,000
Long-term borrowings —current portion (Note 11)	9,517	980,000	1,010,000
Capital lease obligations—current portion (Note 9)	36,444	3,753,026	3,505,471
Accounts payable —trade (Notes 6 and 22)	111,591	11,491,666	10,973,120
Accounts payable —other	10,201	1,050,429	949,264
Income taxes payable (Note 12)	10,482	1,079,480	1,669,849
Accrued expenses	19,941	2,053,550	2,266,427
Deferred income―current	15,154	1,560,603	1,806,074
Other current liabilities (Notes 10 and 12)	10,664	1,098,173	803,902
Total current liabilities	315,274	32,466,927	32,384,107
LONG-TERM BORROWINGS (Note 11)	'	'	980,000
CAPITAL LEASE OBLIGATIONS—Noncurrent (Note 9)	44,701	4,603,322	5,370,365
ACCRUED RETIREMENT AND PENSION COSTS― Noncurrent (Note 13)	22,087	2,274,540	2,112,085
DEFERRED TAX LIABILITIES―Noncurrent (Note 12)	10,613	1,092,863	412,132
DEFERRED INCOME―Noncurrent	26,329	2,711,347	2,562,208
OTHER NONCURRENT LIABILITIES	5,214	536,950	656,191
Total liabilities	424,218	43,685,949	44,477,088
COMMITMENTS AND CONTINGENCIES (Note 17)	'	'	'
SHAREHOLDERS' EQUITY (Notes 4, 13, 14 and 15):	'	'	'
Common stock—authorized, 75,520,000 shares; issued and outstanding, 41,295,600 and 46,697,800 shares at March 31, 2013 and 2014, respectively	247,592	25,497,022	16,833,847
Additional paid-in capital	349,214	35,961,995	27,300,325
Accumulated deficit	-27,846	-2,867,548	-6,399,088
Accumulated other comprehensive income	16,632	1,712,786	263,770
Treasury stock—758,800 and 758,709 shares held by the company at March 31, 2013 and 2014, respectively	-3,807	-392,070	-392,079
Total Internet Initiative Japan Inc. shareholders' equity	581,785	59,912,185	37,606,775
NONCONTROLLING INTERESTS	2,606	268,441	27,403
Total equity	584,391	60,180,626	37,634,178
TOTAL	$1,008,609	¥ 103,866,575	¥ 82,111,266

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parentheticals)	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013
In Thousands, except Share data, unless otherwise specified	USD ($)	JPY (¥)	JPY (¥)	Current [Member]	Current [Member]	Current [Member]
				USD ($)	JPY (¥)	JPY (¥)
Accounts receivable, allowance for doubtful accounts (in Yen and Dollars)	$523	¥ 53,871	¥ 93,934	'	'	'
Other current assets, allowance for doubtful accounts (in Yen and Dollars)	'	'	'	7	720	10,732
Other assets, allowance for doubtful accounts (in Yen and Dollars)	$610	¥ 62,800	¥ 71,727	'	'	'
Common stock, shares authorized	75,520,000	75,520,000	75,520,000	'	'	'
Common stock, shares issued	46,697,800	46,697,800	41,295,600	'	'	'
Common stock, shares outstanding	46,697,800	46,697,800	41,295,600	'	'	'
Treasury stock, shares	758,709	758,709	758,800	'	'	'

Consolidated_Statements_of_Inc

Consolidated Statements of Income

12 Months Ended

In Thousands, except Per Share data, unless otherwise specified

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

Internet Connectivity Services (Corporate Use) [Member]

Internet Connectivity Services (Corporate Use) [Member]

Internet Connectivity Services (Corporate Use) [Member]

Internet Connectivity Services (Corporate Use) [Member]

Internet Connectivity Services (Home Use) [Member]

Internet Connectivity Services (Home Use) [Member]

Internet Connectivity Services (Home Use) [Member]

Internet Connectivity Services (Home Use) [Member]

WAN Services [Member]

WAN Services [Member]

WAN Services [Member]

WAN Services [Member]

Outsourcing Services [Member]

Outsourcing Services [Member]

Outsourcing Services [Member]

Outsourcing Services [Member]

Systems Construction [Member]

Systems Construction [Member]

Systems Construction [Member]

Systems Construction [Member]

Systems Operation And Maintenance [Member]

Systems Operation And Maintenance [Member]

Systems Operation And Maintenance [Member]

Systems Operation And Maintenance [Member]

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

Network services:

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Network services

$653,386

¥ 67,285,729

¥ 65,232,398

¥ 63,409,406

$161,052

¥ 16,585,175

¥ 16,027,134

¥ 14,706,511

$58,502

¥ 6,024,560

¥ 5,466,198

¥ 5,717,417

$242,823

¥ 25,005,867

¥ 25,168,425

¥ 25,666,524

$191,009

¥ 19,670,127

¥ 18,570,641

¥ 17,318,954

'

'

'

'

'

'

'

'

Systems integration:

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Systems integration

412,406

42,469,565

37,205,096

31,469,321

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

181,333

18,673,638

15,824,938

11,997,680

231,073

23,795,927

21,380,158

19,471,641

Equipment sales

16,413

1,690,225

1,490,906

1,111,722

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

ATM operation business

27,450

2,826,832

2,320,086

1,324,156

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total revenues

1,109,655

114,272,351

106,248,486

97,314,605

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

COSTS AND EXPENSES (Notes 6, 9, 13 and 22):

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Cost of network services

515,108

53,045,814

50,692,190

49,984,821

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Cost of systems integration

354,538

36,510,328

30,424,802

24,978,607

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Cost of equipment sales

14,824

1,526,618

1,318,344

980,279

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Cost of ATM operation business

20,617

2,123,168

1,959,597

1,382,194

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total costs

905,087

93,205,928

84,394,933

77,325,901

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Sales and marketing (Note 21)

83,003

8,547,693

8,058,481

7,946,852

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

General and administrative (Note 7)

61,896

6,374,057

5,632,430

5,299,608

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Research and development

4,092

421,361

410,000

388,761

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total costs and expenses

1,054,078

108,549,039

98,495,844

90,961,122

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

OPERATING INCOME

55,577

5,723,312

7,752,642

6,353,483

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

OTHER INCOME (EXPENSES):

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Dividend income

495

51,003

47,117

48,269

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest income

260

26,719

25,708

34,602

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest expense

-2,489

-256,371

-287,314

-299,271

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Foreign exchange gain (loss), net

2,130

219,381

112,136

-4,549

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Net gain (loss) on sales of other investments (Note 4)

1,045

107,655

13,565

-3,154

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Net gain on other investments (Note 4)

3,043

313,393

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Impairment of other investments (Note 4)

'

'

-19,788

-159,592

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Other—net

872

89,799

112,798

6,432

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Other income (expenses)—net

5,356

551,579

4,222

-377,263

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

INCOME FROM OPERATIONS BEFORE INCOME TAX EXPENSE AND EQUITY IN NET INCOME OF EQUITY METHOD INVESTEES

60,933

6,274,891

7,756,864

5,976,220

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

INCOME TAX EXPENSE (Note 12)

17,433

1,795,305

2,607,582

2,525,486

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

EQUITY IN NET INCOME OF EQUITY METHOD INVESTEES (Note 6)

1,981

204,046

168,065

123,776

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

NET INCOME

45,481

4,683,632

5,317,347

3,574,510

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

LESS: NET (INCOME) LOSS ATTRIBUTABLE TO NONCONTROLLING INTERESTS

-2,344

-241,395

-16,693

66,453

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

NET INCOME ATTRIBUTABLE TO INTERNET INITIATIVE JAPAN INC.

$43,137

¥ 4,442,237

¥ 5,300,654

¥ 3,640,963

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

BASIC NET INCOME ATTRIBUTABLE TO INTERNET INITIATIVE JAPAN INC. PER COMMON SHARE (in Yen per share and Dollars per share)

$0.97

¥ 100.26

¥ 130.76

¥ 89.82

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

DILUTED NET INCOME ATTRIBUTABLE TO INTERNET INITIATIVE JAPAN INC. PER COMMON SHARE (in Yen per share and Dollars per share)

$0.97

¥ 100.14

¥ 130.65

¥ 89.78

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Consolidated_Statements_of_Inc1

Consolidated Statements of Income	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
NET INCOME ATTRIBUTABLE TO INTERNET INITIATIVE JAPAN INC. PER SHARE (Note 16):	'	'	'
Basic weighted-average number of common shares outstanding	44,306,680	40,536,800	40,536,800
Diluted weighted-average number of common shares outstanding	44,361,083	40,572,600	40,556,400

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
	USD ($)	JPY (¥)	JPY (¥)	JPY (¥)
NET INCOME	$45,481	¥ 4,683,632	¥ 5,317,347	¥ 3,574,510
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX (Note 15):	'	'	'	'
Foreign currency translation adjustments	4,074	419,557	90,014	-9,539
Unrealized holding gain on securities	9,596	988,139	256,521	102,745
Defined benefit pension plans	399	41,115	-59,252	-31,605
TOTAL COMPREHENSIVE INCOME	59,550	6,132,443	5,604,630	3,636,111
LESS: COMPREHENSIVE (INCOME) LOSS ATTRIBUTABLE TO NONCONTROLLING INTERESTS	-2,343	-241,251	-16,673	66,453
COMPREHENSIVE INCOME ATTRIBUTABLE TO INTERNET INITIATIVE JAPAN INC.	$57,207	¥ 5,891,192	¥ 5,587,957	¥ 3,702,564

Consolidated_Statements_of_Sha

Consolidated Statements of Shareholders' Equity

Retained Earnings [Member]

Retained Earnings [Member]

Accumulated Other Comprehensive Income (Loss) [Member]

Accumulated Other Comprehensive Income (Loss) [Member]

Common Stock [Member]

Common Stock [Member]

Treasury Stock [Member]

Treasury Stock [Member]

Additional Paid-in Capital [Member]

Additional Paid-in Capital [Member]

Noncontrolling Interest [Member]

Noncontrolling Interest [Member]

Total

Total

In Thousands, except Share data

USD ($)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

Balance at Mar. 31, 2011

'

¥ (14,023,259)

'

¥ (85,134)

'

¥ 16,833,847

'

¥ (392,079)

'

¥ 27,318,912

'

¥ (10,937)

'

¥ 29,641,350

Balance (in Shares) at Mar. 31, 2011

'

'

'

'

'

41,295,600

'

'

'

'

'

'

'

'

Purchase of noncontrolling interests in consolidated subsidiaries (Note 14)

'

'

'

'

'

'

'

'

'

-19,395

'

19,390

'

-5

Subsidiary stock issuance (Note 14)

'

'

'

'

'

'

'

'

'

-66,042

'

66,042

'

'

Stock-based compensation

'

'

'

'

'

'

'

'

'

26,843

'

'

'

26,843

Net income

'

3,640,963

'

'

'

'

'

'

'

'

'

-66,453

'

3,574,510

Other comprehensive income (loss), net of tax

'

'

'

61,601

'

'

'

'

'

'

'

'

'

61,601

Dividends paid

'

-608,052

'

'

'

'

'

'

'

'

'

'

'

-608,052

Balance at Mar. 31, 2012

'

-10,990,348

'

-23,533

'

16,833,847

'

-392,079

'

27,260,318

'

8,042

'

32,696,247

Balance (in Shares) at Mar. 31, 2012

'

'

'

'

'

41,295,600

'

'

'

'

'

'

'

'

Acquisition and establishment of new consolidated subsidiaries

'

'

'

'

'

'

'

'

'

'

'

2,688

'

2,688

Stock-based compensation

'

'

'

'

'

'

'

'

'

40,007

'

'

'

40,007

Net income

'

5,300,654

'

'

'

'

'

'

'

'

'

16,693

'

5,317,347

Other comprehensive income (loss), net of tax

'

'

'

287,303

'

'

'

'

'

'

'

-20

'

287,283

Dividends paid

'

-709,394

'

'

'

'

'

'

'

'

'

'

'

-709,394

Balance at Mar. 31, 2013

-62,139

-6,399,088

2,561

263,770

163,467

16,833,847

-3,807

-392,079

265,103

27,300,325

266

27,403

365,451

37,634,178

Balance (in Shares) at Mar. 31, 2013

'

'

'

'

41,295,600

'

'

'

'

'

'

'

'

'

Acquisition of noncontrolling interests in consolidated subsidiaries (Note 14)

'

'

1

61

'

'

0

53

2

99

-3

-213

'

'

Issuance of common stock, net of issuance cost (Note 14)

'

'

'

'

84,110

8,661,600

'

'

83,604

8,609,604

'

'

167,714

17,271,204

Issuance of common stock, net of issuance cost (Note 14) (in Shares)

'

'

'

'

5,400,000

'

'

'

'

'

'

'

'

'

Issuance of common stock upon exercise of stock options

'

'

'

'

15

1,575

'

'

16

1,576

'

'

31

3,151

Issuance of common stock upon exercise of stock options (in Shares)

'

'

'

'

2,200

'

'

'

'

'

'

'

2,200

'

Stock-based compensation

'

'

'

'

'

'

'

'

489

50,391

'

'

489

50,391

Net income

43,137

4,442,237

'

'

'

'

'

'

'

'

2,344

241,395

45,481

4,683,632

Other comprehensive income (loss), net of tax

'

'

14,070

1,448,955

'

'

'

'

'

'

-1

-144

14,069

1,448,811

Dividends paid

-8,844

-910,697

'

'

'

'

'

'

'

'

'

'

-8,844

-910,697

Purchase of treasury stock

'

'

'

'

'

'

0

-44

'

'

'

'

0

-44

Balance at Mar. 31, 2014

($27,846)

¥ (2,867,548)

$16,632

¥ 1,712,786

$247,592

¥ 25,497,022

($3,807)

¥ (392,070)

$349,214

¥ 35,961,995

$2,606

¥ 268,441

$584,391

¥ 60,180,626

Balance (in Shares) at Mar. 31, 2014

'

'

'

'

46,697,800

'

'

'

'

'

'

'

'

'

Consolidated_Statements_of_Sha1

Consolidated Statements of Shareholders' Equity

Retained Earnings [Member]

Retained Earnings [Member]

Accumulated Other Comprehensive Income (Loss) [Member]

Accumulated Other Comprehensive Income (Loss) [Member]

Common Stock [Member]

Common Stock [Member]

Treasury Stock [Member]

Treasury Stock [Member]

Additional Paid-in Capital [Member]

Additional Paid-in Capital [Member]

Noncontrolling Interest [Member]

Noncontrolling Interest [Member]

Total

Total

In Thousands

USD ($)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

Balance at Mar. 31, 2011

'

¥ (14,023,259)

'

¥ (85,134)

'

¥ 16,833,847

'

¥ (392,079)

'

¥ 27,318,912

'

¥ (10,937)

'

¥ 29,641,350

Stock-based compensation (Note 14)

'

'

'

'

'

'

'

'

'

26,843

'

'

'

26,843

Net income

'

3,640,963

'

'

'

'

'

'

'

'

'

-66,453

'

3,574,510

Other comprehensive income, net of tax

'

'

'

61,601

'

'

'

'

'

'

'

'

'

61,601

Dividends paid (Note 14)

'

-608,052

'

'

'

'

'

'

'

'

'

'

'

-608,052

Balance at Mar. 31, 2012

'

-10,990,348

'

-23,533

'

16,833,847

'

-392,079

'

27,260,318

'

8,042

'

32,696,247

Stock-based compensation (Note 14)

'

'

'

'

'

'

'

'

'

40,007

'

'

'

40,007

Net income

'

5,300,654

'

'

'

'

'

'

'

'

'

16,693

'

5,317,347

Other comprehensive income, net of tax

'

'

'

287,303

'

'

'

'

'

'

'

-20

'

287,283

Dividends paid (Note 14)

'

-709,394

'

'

'

'

'

'

'

'

'

'

'

-709,394

Balance at Mar. 31, 2013

-62,139

-6,399,088

2,561

263,770

163,467

16,833,847

-3,807

-392,079

265,103

27,300,325

266

27,403

365,451

37,634,178

Acquisition of noncontrolling interests in consolidated subsidiaries (Note 14)

'

'

1

61

'

'

0

53

2

99

-3

-213

'

'

Issuance of common stock, net of issuance cost (Note 14)

'

'

'

'

84,110

8,661,600

'

'

83,604

8,609,604

'

'

167,714

17,271,204

Issuance of common stock upon exercise of stock options

'

'

'

'

15

1,575

'

'

16

1,576

'

'

31

3,151

Stock-based compensation (Note 14)

'

'

'

'

'

'

'

'

489

50,391

'

'

489

50,391

Net income

43,137

4,442,237

'

'

'

'

'

'

'

'

2,344

241,395

45,481

4,683,632

Other comprehensive income, net of tax

'

'

14,070

1,448,955

'

'

'

'

'

'

-1

-144

14,069

1,448,811

Dividends paid (Note 14)

-8,844

-910,697

'

'

'

'

'

'

'

'

'

'

-8,844

-910,697

Purchase of treasury stock

'

'

'

'

'

'

0

-44

'

'

'

'

0

-44

Balance at Mar. 31, 2014

($27,846)

¥ (2,867,548)

$16,632

¥ 1,712,786

$247,592

¥ 25,497,022

($3,807)

¥ (392,070)

$349,214

¥ 35,961,995

$2,606

¥ 268,441

$584,391

¥ 60,180,626

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
	USD ($)	JPY (¥)	JPY (¥)	JPY (¥)
OPERATING ACTIVITIES:	'	'	'	'
Net income	$45,481,000	¥ 4,683,632,000	¥ 5,317,347,000	¥ 3,574,510,000
Adjustments to reconcile net income to net cash provided by operating activities:	'	'	'	'
Depreciation and amortization	85,677,000	8,822,981,000	7,507,808,000	7,143,631,000
Impairment loss on intangible assets	'	'	48,000,000	37,000,000
Provision for retirement and pension costs, less payments	2,200,000	226,599,000	213,963,000	187,287,000
Provision for (reversal of) allowance for doubtful accounts	-456,000	-46,935,000	-10,712,000	82,046,000
Loss on disposal of property and equipment	811,000	83,487,000	14,638,000	62,368,000
Net (gain) loss on sales of other investments	-1,045,000	-107,655,000	-13,565,000	3,154,000
Net gain on other investments	-3,043,000	-313,393,000	'	'
Impairment of other investments	'	'	19,788,000	159,592,000
Foreign exchange losses (gains), net	-1,262,000	-129,916,000	-55,983,000	14,202,000
Equity in net income of equity method investees	-1,981,000	-204,046,000	-168,065,000	-123,776,000
Deferred income tax expense (benefit)	-6,796,000	-699,826,000	-527,128,000	35,714,000
Others	694,000	71,448,000	39,377,000	67,470,000
Changes in operating assets and liabilities net of effects from acquisition of a company:	'	'	'	'
Decrease (increase) in accounts receivable	-3,325,000	-342,391,000	-2,906,215,000	626,783,000
Decrease in net investment in sales-type lease―noncurrent	1,411,000	145,266,000	37,406,000	330,961,000
Increase in inventories	-3,550,000	-365,533,000	-492,022,000	-85,490,000
Increase in prepaid expenses	-5,951,000	-612,802,000	-635,031,000	-168,860,000
Decrease (increase) in other current and noncurrent assets	-17,493,000	-1,801,403,000	-1,295,279,000	92,932,000
Increase (decrease) in accounts payable	4,631,000	476,860,000	1,881,105,000	-2,928,912,000
Increase (decrease) in income taxes payable	-5,776,000	-594,782,000	-545,914,000	1,842,553,000
Increase in deferred income― noncurrent	888,000	91,462,000	1,015,049,000	276,175,000
Increase (decrease) in accrued expenses, other current and noncurrent liabilities	-5,789,000	-596,174,000	194,201,000	429,998,000
Net cash provided by operating activities	85,326,000	8,786,879,000	9,638,768,000	11,659,338,000
INVESTING ACTIVITIES:	'	'	'	'
Purchases of property and equipment	-88,600,000	-9,123,998,000	-5,588,815,000	-6,167,434,000
Proceeds from sales of property and equipment	4,431,000	456,330,000	543,978,000	350,136,000
Purchases of available-for-sale securities	-1,627,000	-167,545,000	-48,903,000	-269,218,000
Purchases of other investments	-11,517,000	-1,185,985,000	-467,622,000	-186,115,000
Investment in an equity method investee	-1,941,000	-199,920,000	-100,000,000	-24,647,000
Proceeds from sales of available-for-sale securities	3,805,000	391,814,000	0	226,346,000
Proceeds from sales of other investments	3,416,000	351,740,000	109,944,000	94,285,000
Payments of guarantee deposits	-6,690,000	-688,902,000	-164,417,000	-39,403,000
Refund of guarantee deposits	196,000	20,233,000	17,349,000	26,045,000
Payments for refundable insurance policies	-182,000	-18,787,000	-737,000	-6,604,000
Refund from insurance policies	156,000	16,026,000	'	42,948,000
Acquisition of a newly controlled company, net of cash acquired (Note 2)	'	'	-229,058,000	'
Other	-522,000	-53,766,000	-17,620,000	-594,000
Net cash used in investing activities	-99,075,000	-10,202,760,000	-5,945,901,000	-5,954,255,000
FINANCING ACTIVITIES:	'	'	'	'
Proceeds from issuance of short-term borrowings with initial maturities over three months and long-term borrowings	2,427,000	250,000,000	71,000,000	3,370,000,000
Repayments of short-term borrowings with initial maturities of over three months and long-term borrowings	-12,235,000	-1,260,000,000	-1,081,000,000	-620,000,000
Principal payments under capital leases	-38,539,000	-3,968,724,000	-3,678,940,000	-3,425,680,000
Net increase (decrease) in short-term borrowings	'	'	400,000,000	-4,180,000,000
Proceeds from issuance of subsidiary stock to noncontrolling interests	'	'	2,570,000	'
Dividends paid	-8,844,000	-910,697,000	-709,394,000	-608,052,000
Proceeds from issuance of common stock, net of issuance cost	167,714,000	17,271,204,000	'	'
Other	2,000	109,000	'	'
Net cash provided by (used in) financing activities	110,525,000	11,381,892,000	-4,995,764,000	-5,463,732,000
FORWARD	96,776,000	9,966,011,000	-1,302,897,000	241,351,000
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	1,906,000	196,217,000	24,945,000	-18,142,000
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	98,682,000	10,162,228,000	-1,277,952,000	223,209,000
CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR	119,041,000	12,258,872,000	13,536,824,000	13,313,615,000
CASH AND CASH EQUIVALENTS, END OF YEAR	217,723,000	22,421,100,000	12,258,872,000	13,536,824,000
ADDITIONAL CASH FLOW INFORMATION:	'	'	'	'
Interest paid	2,493,000	256,722,000	287,158,000	297,862,000
Income taxes paid	26,294,000	2,707,784,000	3,527,987,000	481,580,000
NONCASH INVESTING AND FINANCING ACTIVITIES:	'	'	'	'
Acquisition of assets by entering into capital leases	33,368,000	3,436,245,000	4,816,248,000	4,749,695,000
Facilities purchase liabilities	10,200,000	1,050,429,000	949,264,000	659,266,000
Asset retirement obligation	1,659,000	170,814,000	26,620,000	42,273,000
Acquisition of a company (Note 2):	'	'	'	'
Assets acquired	'	'	404,139,000	'
Liabilities assumed	'	'	104,321,000	'
Noncontrolling interests	'	'	118,000	'
Cash paid	'	'	-299,700,000	'
Cash acquired	'	'	70,642,000	'
Acquisition of a newly controlled company, net of cash acquired	'	'	¥ (229,058,000)	'

Note_1_Description_of_Business

Note 1 - Description of Business and Summary of Significant Accounting Policies	12 Months Ended
	Mar. 31, 2014
Accounting Policies [Abstract]	'
Organization, Consolidation and Presentation of Financial Statements Disclosure and Significant Accounting Policies [Text Block]	'
	1	DESCRIPTION OF BUSINESS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
	Internet Initiative Japan Inc. ("IIJ," a Japanese corporation) was founded in December 1992 to develop and operate Internet access services and other Internet-related services in Japan. As of March 31, 2014, 26.4% of IIJ’s voting shares were jointly owned by Nippon Telegraph and Telephone Corporation ("NTT") and its subsidiary. IIJ and its subsidiaries (collectively, the "Company") provide customers substantially operating in Japan with Internet connectivity services, WAN services and outsourcing services.  The Company also provides systems integration which consists of systems construction and systems operation and maintenance. In addition, a consolidated subsidiary provides Automated Teller Machines ("ATM") operation services.
	Certain Significant Risks and Uncertainties
	The Company relies on telecommunications carriers for a significant portion of its network backbone and on regional NTT subsidiaries, electric power companies and their affiliates for local connections to customers. Currently, NTT Communications Corporation, a wholly owned subsidiary of NTT, is the largest provider of network infrastructure for the Company. The Company believes that its use of multiple carriers and suppliers significantly mitigates the risk of damages from service disruptions. However, any disruption of telecommunication services could have an adverse effect on operating results.
	Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of accounts receivable, which includes the accounts receivable from a large customer as noted in Note 20. The Company's management believes that the risks associated with accounts receivable is mitigated by the large number of customers comprising its customer base and its credit line control. The Company also conducts an evaluation of a new customer’s financial condition at the inception of a transaction and continuously monitors delays in payment for each customer.
	Summary of Significant Accounting Policies
	Basis of Presentation—IIJ maintains its records and prepares its financial statements in accordance with generally accepted accounting principles in Japan. Certain adjustments and reclassifications have been incorporated in the accompanying consolidated financial statements to conform to generally accepted accounting principles in the United States of America ("U.S. GAAP"). These adjustments were not recorded in the statutory accounts.
	Reclassification－Certain reclassifications have been made to prior periods to conform to the current year presentations: (1) “Guarantee deposits―current,” which had been previously included in "Other current assets," was separately disclosed as the amount was deemed material. (2) “Increase in inventories, prepaid expenses and other current and noncurrent assets” was divided into “Increase in inventories”, “Increase in prepaid expenses” and “Increase in other current and noncurrent assets” as the amounts were deemed material.
	Translation into U.S. Dollars—IIJ maintains its accounts in Japanese yen, the currency of the country in which it is incorporated and principally operates. The U.S. dollar amounts included herein represent a translation using the noon buying rate in New York City for cable transfers in yen as certified for customs purposes by the Federal Reserve Bank of New York at March 31, 2014 of ¥102.98 =160;$1, solely for the convenience of the reader. The translation should not be construed as a representation that the yen amounts have been, could have been, or could in the future be converted into U.S. dollars.
	Consolidation—The consolidated financial statements include the accounts of IIJ and all of its subsidiaries, Net Care, Inc. ("Net Care"), IIJ America, Inc. ("IIJ-America"), Netchart Japan Inc. ("NCJ"), hi-ho Inc. ("hi-ho"), Trust Networks Inc. ("Trust Networks"), IIJ Innovation Institute Inc. ("IIJ-II"), IIJ Global Solutions Inc. ("IIJ-Global") and its subsidiaries, IIJ Exlayer Inc. ("IIJ-Exlayer") and its subsidiaries and IIJ Europe Limited ("IIJ-Europe"). IIJ-Global was acquired by IIJ on September 1, 2010. IIJ-Exlayer was acquired by IIJ on April 2, 2012. IIJ-Europe was originally a wholly-owned subsidiary of IIJ-Exlayer. IIJ-Exlayer was merged with IIJ on January 1, 2014. GDX Japan Inc. (“GDX”) was established on April 16, 2007 and liquidated on March 16, 2012. All of the subsidiaries, except for IIJ-Exlayer, IIJ-America, IIJ-Europe and other foreign subsidiaries, have fiscal years ending March 31. IIJ-Exlayer, IIJ-America, IIJ-Europe and other foreign subsidiaries’ fiscal year-end is December 31 and such date was used for purposes of preparing the consolidated financial statements as it is not practicable for the foreign subsidiaries to report their financial results as of March 31. There were no significant events that occurred during the intervening period that would require adjustment to or disclosure in the accompanying consolidated financial statements. Intercompany transactions and balances have been eliminated in consolidation.
	Investments in companies over which IIJ has significant influence but not control are accounted for by the equity method. For other than a temporary decline in the value of investments in equity method investees below the carrying amount, the investment is reduced to fair value and an impairment loss is recognized.
	Equity-method goodwill which is the portion of the difference between the cost of an investment and the amount of underlying equity in net assets of an investee is not amortized, but equity-method investments shall continue to be reviewed for impairment in accordance with Accounting Standards Codification (“ASC”)  323 “Investments-Equity Method and Joint Ventures.”
	A subsidiary or equity method investee may issue its shares to third parties at amounts per share in excess of or less than the Company’s average per share carrying value. Changes in a parent’s ownership interest while the parent retains its controlling financial interest in its subsidiary are accounted for as equity transactions.
	Use of Estimates—The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting period. Significant estimates and assumptions used are primarily in the areas of evaluation of investments, valuation allowances for deferred tax assets, allowance for doubtful accounts, determination of pension benefit costs and obligations, estimated useful lives of fixed assets and intangible assets with finite useful lives and impairment of long-lived assets, goodwill and intangible assets deemed to have indefinite useful lives. Actual results could differ from those estimates.
	Revenue Recognition—Network service revenues are billed and recognized monthly on a straight-line basis. Initial set up fees received in connection with network services are deferred and recognized over the estimated average period of the subscription for each service.
	System integration and service arrangements involve the following deliverables:
		●	System construction services ― include all or some of the following elements depending on arrangements to meet each of our customer's requirements: consulting, project planning, system design, and development of network systems. These services also include the installation of software as well as configuration and installationof hardware.
		●	Software ― we resell third-party software such as Oracle and Windows to our customers, which are installed by us during the system development process.
		●	Hardware ― we also resell third-party hardware, primarily servers, switches and routers, which we install during the system development process. The hardware is generic hardware that is often sold by third party manufacturers and resellers.
		●	Monitoring and operating service ― we monitor our customer's network activity and internet connectivity to detect and report problems. We also provide constant data backup services.
		●	Hardware and software maintenance service ― we repair or replace any malfunctioning parts of hardware. We examine software faults and provide suitable solutions to customers.
	The system construction services are generally delivered over a three-month period. All hardware and software are delivered and installed during this period. Customers are required to pay a specified fixed fee that is not payable until after the system construction has been completed and accepted by our customers.
	Monitoring, operating, and hardware and software maintenance services generally commence once our customers have accepted the systems, and contract periods are generally from one to five years. Our contracts include a stated annual fee for these services.
	For multiple-element arrangements that include system construction service, hardware, software essential to the hardware product’s functionality and undelivered non-software services (e.g., monitoring and operating services), the Company allocates revenue to all deliverables based on their relative selling prices. The Company uses a hierarchy to determine the selling price to be used for allocating revenue to deliverables: (i) vendor-specific objective evidence of fair value (“VSOE”), (ii) third-party evidence of selling price (“TPE”) and (iii) best estimate of the selling price (“ESP”). The allocation of revenue is based mainly on the Company’s ESPs except for certain undelivered non-software services for which VSOE has been established. The Company’s process for determining its ESP for deliverables includes various factors that may vary depending on the circumstances and specific characteristics related to each deliverable. In developing the ESP, the Company considers customer demand, the existence and effect of competitors, general profit margin realized in the marketplace, volume of the transactions, the Company’s internal costs of providing the deliverables, the profit objectives including targeted and historical margins realized on similar sales to similar customers and the historical pricing practices.
	The method used to account for each unit and the period over which each unit of accounting is recognized are as follows:
		●	Revenue allocated to system construction services is accounted for using contract accounting. System construction service revenues, which are generally completed within three months, are recognized based on the completed-contract method in compliance with ASC 605-35-25-92 because the Company is unable to bill customers and the title to the constructed network system is not transferred to the customers unless they are satisfied with and accept the completed systems.
		●	Revenue related to the hardware and software essential to the hardware product’s functionality is not recognized until customer acceptance is received because title to the hardware and software do not transfer to our customers until formal acceptance is received.
		●	Revenue related to undelivered non-software services (monitoring, operating and hardware maintenance services) is recognized on a straight-line basis over the contract period.
	The Company also enters into multiple-element arrangements for system integration services that include software not essential to the hardware product’s functionality and software-related services and account for them in accordance with ASC 985-605, “Software-Revenue Recognition”. The Company has been able to establish VSOE of fair value of the software-related services based on separate renewal contracts of the services that are consistently priced within a narrow range. The Company allocates revenue to such services based on VSOE and recognizes the revenues on a straight-line basis over the contract period. The Company allocates the residual amount to the software and system construction services.
	Equipment sales revenues are recognized when equipment is delivered and accepted by the customer.
	The Company evaluates whether it is appropriate to record the gross amount of revenues and related costs or the net amount earned in reporting system construction services and equipment sales, depending on whether the Company functions as principal or agent.
	ATM operation business revenues consist primarily of commissions for each withdrawing transaction with the use of ATMs. ATM commission collected from each withdrawal is aggregated every month and recognized as ATM operation revenues.
	Revenue is recognized net of consumption tax collected from customers and subsequently remitted to governmental authorities.
	Cash and Cash Equivalents—Cash and cash equivalents includes time deposit with original maturities of three months or less.
	Allowance for Doubtful Accounts—An allowance for doubtful accounts is established in amounts considered to be appropriate based primarily upon the Company's past credit loss experience and an evaluation of potential losses in the receivables outstanding.
	Other Investments—The Company classifies its marketable equity securities as available-for-sale securities, which are accounted for at fair value with unrealized gains and losses excluded from earnings and reported in accumulated other comprehensive income (loss). The cost of securities sold is determined based on average cost.
	The Company reviews the fair value of available-for-sale securities on a regular basis to determine if the fair value of any individual security has declined below its cost and if such decline is other-than-temporary.  If the decline in value is judged to be other-than-temporary, the cost basis of the investment is written down to fair value. Other-than-temporary declines in value are determined taking into consideration the extent of decline in fair value, the length of time that the decline in fair value below cost has existed and events that might accelerate the recognition of impairment. The resulting realized loss is included in the consolidated statements of income in the period in which the decline is deemed to be other-than-temporary.
	Non-marketable equity securities are carried at cost as fair value is not readily determinable. When the Company evaluates whether non-marketable equity securities are impaired or not, the Company evaluates first whether an event or change in circumstances has occurred in the period that may have significant adverse effect on the fair value of the securities (an impairment indicator). The Company uses such impairment indicators as follows:
		●	A significant deterioration in the earnings performance or business prospects of the investee.
		●	A significant adverse change in the regulatory, economic, or technological environment of the investee.
		●	A significant adverse change in the general market condition of either the geographic area or the industry in which the investee operates.
		●	A recent example of the new issuance of a security, in which the issue price is less than our cost.
	The Company estimates the fair value of the non-marketable equity securities when an impairment indicator is present. The fair value is determined as a result of considering various unobservable inputs which are available to the Company, including expectation of future income of the investees, net asset value of the investees, and material unrealized losses to be considered in assets and liabilities held by the investees. The Company recognizes impairment of non-marketable equity securities when the fair value is below the carrying amount and the decline in fair value is considered to be other-than-temporary.
	Inventories—Inventories consist mainly of network equipment purchased for resale and work-in-process for construction of network systems. Network equipment purchased for resale is stated at the lower of cost, which is determined by the average-cost method, or market.  Work-in-process for development of network systems is stated at the lower of actual production costs, including overhead cost, or market.  Inventories are reviewed periodically and items considered to be slow-moving or obsolete are written down to their estimated net realizable value.
	Leases—Capital leases are capitalized at the inception of the lease at the present value of the minimum lease payments. All other leases are accounted for as operating leases. Lease payments for capital leases are apportioned to interest expense and a reduction of the lease liability so as to achieve a constant rate of interest on the remaining balance of the liability. Operating lease payments are recognized as an expense on a straight-line basis over the lease term.
	Sales-Type Leases—The Company has some sales-type lease agreements with customers. The Company recognizes revenues on sales-type leases when the assets under lease are delivered to and accepted by the customers. The revenue recognized is calculated at the net present value of the future receipt amounts. Interest income in sales-type leases is recognized in other income using the interest method.
	Property and Equipment—Property and equipment are recorded at cost. Depreciation and amortization of property and equipment, including capitalized software and capital leases, are computed principally using the straight-line method based on either the estimated useful lives of assets or the lease period, whichever is shorter.
	The useful lives for depreciation and amortization by major asset classes are as follows:
			Range of
			Useful Lives
	Data communications, office and other equipment (years)		3	to	20
	Buildings (years)			20
	Leasehold improvements (years)		8	to	20
	Capitalized software (years)			5
	Capital leases (years)		4	to	6
	Impairment of Long-Lived Assets—Long-lived assets consist principally of property and equipment, including those items leased under capital leases and amortized intangible assets. The Company evaluates the impairment of long-lived assets whenever events or changes in circumstances indicate that the carrying amount of an asset or asset group may not be recoverable. Long-lived assets to be held and used are reviewed for impairment by comparing the carrying amount of the asset or asset group with their estimated undiscounted future cash flows. If the cash flows are determined to be less than the carrying amount of the asset or asset group, an impairment loss has occurred and the loss would be recognized during the period for the difference between the carrying amount of the asset or asset group and estimated fair value.
	Goodwill and Intangible Assets—Goodwill and intangible assets that are deemed to have indefinite useful lives are not amortized, but are subject to impairment testing.  Impairment testing is performed annually or more frequently if events or changes in circumstances indicate that the asset might be impaired. The Company performs annual impairment tests on March 31. If the carrying amount of a reporting unit exceeds its fair value, the Company then performs the second step of the goodwill impairment test to measure the amount of impairment loss, if any. Intangible assets with finite useful lives, consisting of customer relationships, are amortized using a non-straight-line basis based on the pattern of expected future economic benefit over the estimated useful lives, which range from 6 to 19 years.
	Asset Retirement Obligations—The Company records the fair value of a liability for an asset retirement obligation in the period in which it is incurred. When the liability is initially recorded, the Company capitalizes the related cost by increasing the carrying amount of long-lived asset. Over time, the liability is accreted to its present value each period, and the capitalized cost is depreciated for the period the Company has estimated.
	Pension and Severance Indemnities Plans—The Company has defined benefit pension plans and severance indemnities plans. The cost of the pension plans and severance indemnities plans are accrued based on amounts determined using actuarial methods. In addition, the Company has defined contribution pension plans. The costs of defined contribution pension plans are charged to expenses when incurred.
	Income Taxes—Income tax expense is based on reported earnings before income taxes. Deferred income taxes reflect the impact of temporary differences between assets and liabilities recognized for financial reporting purposes and such amounts recognized for tax purposes and tax loss carryforwards. These deferred taxes are measured using the currently enacted tax rates in effect for the year in which the temporary differences or tax loss carryforwards are expected to reverse. Valuation allowances are provided against deferred tax assets when it is more likely than not that a tax benefit will not be realized.
	The Company recognizes the financial statement effect of uncertain tax positions when they are more-likely- than not, based on the technical merits, that the tax positions will be sustained upon examination by the tax authorities. Benefits from tax positions that meet the more-likely-than-not recognition threshold are measured at the largest amount of benefit that is greater than 50% likely of being realized upon settlement. Interest and penalties accrued related to unrecognized tax benefits are included in income tax expense in the consolidated statements of income.
	Foreign Currency Translation—The assets and liabilities of a foreign subsidiary and an equity method investee are translated into Japanese yen at the respective year-end exchange rates. All income and expense accounts are translated at average rates of exchange. The resulting translation adjustments are included in accumulated other comprehensive income.
	Foreign currency assets and liabilities, which consist substantially of cash denominated in U.S. dollars, are stated at the amount as computed by using year-end exchange rates and the resulting transaction gain or loss is recognized in earnings.
Stock Splits―On September 6, 2012, IIJ’s board of directors approved a two hundred-for-one split of IIJ’s common stock. Shareholders of record on September 30, 2012 received an additional common share. The stock split was effective on October 1, 2012. In order to reflect this split, information pertaining to shares and earnings per share has been restated in the accompanying financial statements and related notes.
Stock-Based Compensation—The Company measures and records the compensation cost from stock compensation-type stock option based on fair value. The fair value of the stock option is measured on the date of grant using the Black-Scholes option-pricing model, and amortized over the requisite service period. The compensation cost is mainly included in “General and administrative” expenses.
Research and Development and Capitalized Software Development Costs—Research and development costs are expensed as incurred, which include research and development costs incurred for computer software to be leased. Software development costs incurred subsequent to establishing technological feasibility through the general release of the software products are capitalized. Technological feasibility is demonstrated by the completion of a detailed program design. Capitalized costs are amortized based on either the ratio of the current revenues to the total estimated revenues over the estimated useful lives (generally five years) or the equally allocated amount over the residual useful lives, whichever is larger.
Advertising—Advertising costs are expensed as incurred and are recorded in “Sales and marketing.”
Basic and Diluted Net Income attributable to Internet Initiative Japan Inc. per Common Share—Basic net income attributable to Internet Initiative Japan Inc. per common share is computed by dividing net income attributable to Internet Initiative Japan Inc. by the weighted-average number of shares of common stock outstanding during the year. Diluted net income attributable to Internet Initiative Japan Inc. per common share reflects the potential dilutive effect of stock options.
Other Comprehensive Income (Loss)—Other comprehensive income (loss) consists of translation adjustments resulting from the translation of financial statements of a foreign subsidiary, unrealized gains or losses on available-for-sale securities and defined benefit pension plans adjustment.
Segment Reporting—ASC Topic 280, “Segment Reporting” establishes standards for reporting information about operating segments. Operating segments are defined as components of an enterprise that engage in business activities from which it may earn revenues and incur expense and for which separate financial information is available that is evaluated regularly by the chief operation decision maker in deciding how to allocate resources and in assessing performance.
The Company provides a comprehensive range of network solutions to meet its customers’ needs by cross-selling a variety of services, including Internet connectivity services, WAN services, outsourcing services, systems integration and sales of network-related equipment, and ATM operation services. The Company’s chief operating decision maker, who is the Company’s Chief Operating Officer ("COO"), regularly reviews the revenue and cost of sales on the two operating segments, which are Network service and systems integration business segment, and ATM operation business segment. The COO also makes decisions regarding how to allocate resources and assess performance based on the segments.
New Accounting Guidance
In December 2011, the FASB issued Accounting Standards Update (“ASU”) 2011-11, "Balance Sheet: Disclosures about Offsetting Assets and Liabilities," which requires new disclosures about financial instruments and derivative instruments that are either offset by or subject to an enforceable master netting arrangement or similar agreement. In January 2013, the FASB issued ASU 2013-01, "Balance Sheet: Clarifying the Scope of Disclosures about Offsetting Asset and Liabilities," which clarifies the scope of the offsetting disclosures of ASU 2011-11. Both ASUs are effective for fiscal years beginning on or after January 1, 2013 and interim periods within those years and the Company adopted this ASU in the first quarter beginning April 1, 2013. The adoption of this ASU did not have a material impact on the Company’s financial position or results of operations.
In July 2012, the FASB issued ASU 2012-02, "Intangibles－Goodwill and Other: Testing Indefinite-Lived Intangible Assets for Impairment," which provides new guidance on the annual indefinite-lived intangible assets impairment testing. The objective of the amendments in this Update is to reduce the cost and complexity of performing an impairment test for indefinite-lived intangible assets by simplifying how an entity tests those assets for impairment and to improve consistency in impairment testing guidance among long-lived asset categories. The amendments permit an entity first to assess qualitative factors to determine whether it is more likely than not that an indefinite-lived intangible asset is impaired as a basis for determining whether it is necessary to perform the quantitative impairment test in accordance with Subtopic 350-30, “Intangibles—Goodwill and Other—General Intangibles Other than Goodwill”. This ASU is effective for annual and interim indefinite-lived intangible assets impairment tests performed for fiscal years beginning after September 15, 2012 and the Company adopted this ASU in the first quarter beginning April 1, 2013. The adoption of this ASU did not have a material impact on the Company’s financial position or results of operations.
In February 2013, the FASB issued ASU 2013-02, “Comprehensive Income: Reporting of Amounts Reclassified out of Accumulated Other Comprehensive Income,” which requires entities to provide information about the amounts reclassified out of accumulated other comprehensive income by component, and to present, either on the face of the statement where net income is presented or in the notes, significant amounts reclassified out of accumulated other comprehensive income by the respective line items of net income. This ASU is effective for fiscal years, and interim periods within those years, beginning after December 15, 2012 and the Company adopted this ASU in the first quarter beginning April 1, 2013. The adoption of this ASU did not have a material impact on the Company’s financial position or results of operations. See Note 15 for the disclosures related to this adoption.
Accounting Guidance Issued But Not Adopted as of March 31, 2014
In July 2013, the FASB issued ASU 2013-11, “Income Taxes: Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists,” which defines the presentation requirements of an unrecognized tax benefit, or a portion of an unrecognized tax benefit, in the financial statements. This ASU is effective for fiscal years, and interim periods within those years, beginning after December 15, 2013. Early adoption is permitted and retrospective application is permitted, but not required. The adoption of this ASU will not have a material impact on the Company’s financial position or results of operations.
In May 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers,” to clarify the principles for recognizing revenue and to develop a common revenue standard for U.S.GAAP and International Financial Reporting Standards. This guidance also requires an entity to improve disclosures to enable users of financial statements to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. This ASU is effective for fiscal years, and interim periods within those years, beginning after December 15, 2016. The Company is currently evaluating the impact of adopting this guidance.

Note_2_Business_Combinations

Note 2 - Business Combinations	12 Months Ended
	Mar. 31, 2014
Business Combinations [Abstract]	'
Business Combination Disclosure [Text Block]	'
	2	BUSINESS COMBINATIONS
	On April 2, 2012, the Company acquired 99.9% of the outstanding common shares of Exlayer Global Inc., which was renamed IIJ Exlayer Inc. ("IIJ-Exlayer"), for total consideration of ¥299,700 thousand ($3,183 thousand) paid in cash. There are no future contingent payments. IIJ-Exlayer is a holding company with overseas subsidiaries in the system integration industry. The acquisition of IIJ-Exlayer is expected to help the Company to accelerate its international business development. Pro forma results of operations have not been presented because the effect of the acquisition was not material.
	There were no business acquisitions during the years ended March 31, 2012 and 2014.

Note_3_Inventory

Note 3 - Inventory	12 Months Ended
	Mar. 31, 2014
Inventory Disclosure [Abstract]	'
Inventory Disclosure [Text Block]	'
	3	INVENTORY
	The components of inventories as of March 31, 2013 and 2014 are as follows:
			Thousands of Yen				Thousands of
							U.S. Dollars
			2013		2014		2014
	Network equipment purchased for resale		¥	350,976	¥	503,334	$	4,888
	Work in process			950,708		1,166,924		11,331
	Total inventories		¥	1,301,684	¥	1,670,258	$	16,219

Note_4_Other_Investments

Note 4 - Other Investments	12 Months Ended
	Mar. 31, 2014
Investments, Debt and Equity Securities [Abstract]	'
Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block]	'
	4	OTHER INVESTMENTS
	Pursuant to ASC Topic 320, “Investments―Debt and Equity Securities,” all of the Company's marketable equity securities are classified as available-for-sale securities. Information regarding the securities classified as available-for-sale at March 31, 2013 and 2014 is as follows:
			Thousands of Yen
	31-Mar-13		Cost		Unrealized		Unrealized		Fair
					Gains		Losses		Value
	Available-for-sale—Equity securities		¥	500,616	¥	813,445	¥	4,138	¥	1,309,923
	31-Mar-14
	Available-for-sale—Equity securities		¥	1,391,820	¥	2,364,442	¥	5,251	¥	3,751,011
			Thousands of U.S. Dollars
	31-Mar-14		Cost		Unrealized		Unrealized		Fair
					Gains		Losses		Value
	Available-for-sale—Equity securities		$	13,515	$	22,961	$	51	$	36,425
	The following table provides the fair value and gross unrealized losses of the Company's investments, which have been deemed to be temporarily impaired, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position, as of March 31, 2013 and 2014:
			Thousands of Yen
			Less than				12 Months or More				Total
			12 Months
	31-Mar-13		Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
			Value		Losses		Value		Losses		Value		Losses
	Available-for-sale—Equity securities		¥	27,902	¥	4,138		-		-	¥	27,902	¥	4,138
	31-Mar-14
	Available-for-sale—Equity securities		¥	56,524	¥	5,251		-		-	¥	56,524	¥	5,251
			Thousands of U.S. Dollars
			Less than				12 Months or More				Total
			12 Months
	31-Mar-14		Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
			Value		Losses		Value		Losses		Value		Losses
	Available-for-sale—Equity securities		$	549	$	51		-		-	$	549	$	51
	The Company regularly reviews all of the Company's investments to determine if any are other-than-temporarily impaired. The analysis includes reviewing industry analyst reports, sector credit ratings and volatility of the security's market price.
	The Company’s unrealized loss on investments in marketable equity securities as of March 31, 2014 relates to Japanese companies (6 issuers) in various industries. The fair value of each investment is between 0.6% and 13.4% less than its cost. The duration of the unrealized loss position was less than 12 months. The Company evaluated the near-term prospects of the issuers and the analyst reports in relation to the severity and duration of impairment. Based on that evaluation and the Company’s ability and intent to hold the investments for a reasonable period of time sufficient for a recovery of fair value, the Company does not consider the investments to be other-than-temporarily impaired at March 31, 2014.
	Proceeds from the sale of available-for-sale securities were ¥226,346 thousand, zero and ¥391,814 thousand ($3,805 thousand) for the years ended March 31, 2012, 2013 and 2014, respectively. Gross realized gains of ¥9,140 thousand and  ¥107,655 thousand($1,045 thousand)  were included in "Other income (expenses)" for the years ended March 31, 2012 and 2014, respectively, and gross realized losses of ¥12,293 thousand were included in "Other income (expenses)" for the year ended March 31, 2012.
	Net gain on other investments, which was derived from realized gains on investments in funds, for the year ended March 31, 2014, was ¥313,393 thousand ($3,043 thousand).
	The aggregate cost of the Company’s cost method investments totaled ¥2,461,339 thousand and ¥2,604,806 thousand ($25,294 thousand) at March 31, 2013 and 2014, respectively.
	Impairment of investments in certain marketable equity securities and nonmarketable equity securities, including funds, included in "Other income (expenses)" in the Company’s consolidated statements of income, were recognized to reflect the decline in value considered to be other-than-temporary of ¥87,911 thousand and ¥71,681 thousand, respectively, for the year ended March 31, 2012, ¥19,788 thousand and zero, respectively, for the year ended March 31, 2013.

Note_5_Allowance_for_Doubtful_

Note 5 - Allowance for Doubtful Accounts and Loans	12 Months Ended
	Mar. 31, 2014
Disclosure Text Block Supplement [Abstract]	'
Allowance for Credit Losses [Text Block]	'
	5	ALLOWANCE FOR DOUBTFUL ACCOUNTS AND LOANS
	An analysis of the allowance for doubtful accounts and loans for the years ended March 31, 2012, 2013 and 2014 is as follows:
			Thousands of Yen
			Balance at		Credits			Provision for			Other		Balance at
			Beginning of		Charged Off			(Reversal of)					End of Year
			Year					Doubtful
								Accounts
	Year ended March 31, 2012		¥	142,871	¥	(19,878	)	¥	82,046			-	¥	205,039
	Year ended March 31, 2013		¥	205,039	¥	(17,934	)	¥	(10,712	)		-	¥	176,393
	Year ended March 31, 2014		¥	176,393	¥	(12,067	)	¥	(46,935	)		-	¥	117,391
			Thousands of U.S. Dollars
			Balance at		Credits			Reversal of			Other		Balance at
			Beginning of		Charged Off			Doubtful					End of Year
			Year					Accounts
	Year ended March 31, 2014		$	1,713	$	(117	)	$	(456	)		-	$	1,140

Note_6_Investments_in_Equity_M

Note 6 - Investments in Equity Method Investees	12 Months Ended
	Mar. 31, 2014
Equity Method Investments and Joint Ventures [Abstract]	'
Equity Method Investments and Joint Ventures Disclosure [Text Block]	'
	6	INVESTMENTS IN EQUITY METHOD INVESTEES
	IIJ utilizes various companies in Japan to develop and operate its Internet business. Businesses operated by its equity method investees include multifeed technology services and location facilities for connecting high-speed Internet backbones (Internet Multifeed Co., "Multifeed"), comprehensive portal site operations (Internet Revolution Inc., "i-revo"), point management systems operations (Trinity Inc., "Trinity"), research and software development (Stratosphere Inc., "Stratosphere") and offering cloud-based systems that undergird smartphone applications (Appiaries Corporation, "Appiaries").
	The aggregate amounts of balances and transactions of the Company with these equity method investees as of March 31, 2013 and 2014, and for each of the three years in the period ended March 31, 2014 are summarized as follows:
			Thousands of Yen								Thousands of
											U.S. Dollars
			2012			2013		2014			2014
	Accounts receivable			-		¥	52,422	¥	43,170		$	419
	Accounts payable			-			39,734		40,613			394
	Revenues		¥	624,718			598,765		538,288			5,227
	Costs and expenses			403,400			456,892		451,342			4,383
	The Company's investments in these equity method investees and respective ownership percentage at March 31, 2013 and 2014 consisted of the following:
			Thousands of Yen										Thousands of
													U.S. Dollars
			2013					2014					2014
	Multifeed			33	%	¥	1,141,909		33	%	¥	1,244,512	$	12,085
	i-revo			30			371,888		30			529,142		5,138
	Trinity			33.75			93,154		33.75			88,804		862
	Stratosphere			50			74,772		50			32,451		315
	Appiaries			-			-		49			190,780		1,853
	Total					¥	1,681,723				¥	2,085,689	$	20,253
	The Company also had a loan of ¥20,000 thousand ($194 thousand) to Stratosphere, which was included in the “Other assets” in the Company’s consolidated balance sheets as of March 31, 2014.
	The Company acquired shares in Appiaries for ¥199,920 thousand ($1,941 thousand) in March 2014, which was managed as a joint venture with a certain cloud-based systems operating company.
	As of March 31, 2014, the balance of equity-method goodwill was ¥53,841 thousand  ($523 thousand) and was included in “Investments in equity method investees” in the Company’s consolidated balance sheets.

Note_7_Property_and_Equipment

Note 7 - Property and Equipment	12 Months Ended
	Mar. 31, 2014
Property, Plant and Equipment [Abstract]	'
Property, Plant and Equipment Disclosure [Text Block]	'
	7	PROPERTY AND EQUIPMENT
	Property and equipment as of March 31, 2013 and 2014 consisted of the following:
			Thousands of Yen						Thousands of
									U.S. Dollars
			2013			2014			2014
	Data communications equipment		¥	6,746,069		¥	8,656,572		$	84,061
	Office and other equipment			2,130,160			3,375,846			32,782
	Land			-			532,997			5,176
	Buildings			668,631			1,615,081			15,683
	Leasehold improvements			2,666,584			3,641,072			35,357
	Capitalized software			18,465,716			21,006,728			203,988
	Assets under capital leases, primarily data communications equipment			21,864,989			22,868,800			222,070
	Total			52,542,149			61,697,096			599,117
	Less accumulated depreciation and amortization			(29,516,394	)		(34,725,611	)		(337,207	)
	Property and equipment—net		¥	23,025,755		¥	26,971,485		$	261,910
	Depreciation and amortization expenses for the property and equipment amounted to ¥6,522,033 thousand, ¥6,950,249 thousand and ¥8,359,907 thousand ($81,180 thousand) for the years ended March 31, 2012, 2013 and 2014, respectively.
	The Company recorded losses on disposal of property and equipment of ¥62,368 thousand, ¥14,638 thousand and ¥83,487 thousand ($811 thousand) for the years ended March 31, 2012, 2013 and 2014, respectively, in “General and administrative” expenses in the Company’s consolidated statements of income.
	Capitalized software included internal use software of ¥15,912,108 thousand and ¥17,410,834 thousand ($169,070 thousand) as of  March 31, 2013 and 2014, respectively, and software to be leased of ¥2,553,608 thousand and ¥3,595,894 thousand ($34,918 thousand) as of March 31, 2013 and 2014, respectively.
	The unamortized balance of software to be leased was ¥1,952,450 thousand and ¥2,532,335 thousand ($24,591 thousand) as of March 31, 2013 and 2014, respectively. Amortization expense of software to be leased was ¥208,435 thousand, ¥349,537 thousand and ¥495,050 thousand ($4,807 thousand) for the years ended March 31, 2012, 2013 and 2014, respectively, and was included in cost of systems integration.
	The estimated aggregate amortization expense of software to be leased for each of the next five years is as follows:
	Year Ending March 31		Thousands of Yen			Thousands of
						U.S. Dollars
	2015		¥	619,166		$	6,013
	2016			677,298			6,577
	2017			526,416			5,112
	2018			523,848			5,087
	2019			185,607			1,802

Note_8_Goodwill_and_Other_Inta

Note 8 - Goodwill and Other Intangible Assets	12 Months Ended
	Mar. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]	'
Goodwill and Intangible Assets Disclosure [Text Block]	'
	8	GOODWILL AND OTHER INTANGIBLE ASSETS
	The components of intangible assets as of March 31, 2013 and 2014 are as follows:
			Thousands of Yen						Thousands of
									U.S. Dollars
			2013			2014			2014
	Intangible assets subject to amortization:
	Customer relationships		¥	6,424,471			6,424,471		$	62,386
	Total			6,424,471			6,424,471			62,386
	Less accumulated amortization
	Customer relationships			(1,759,440	)		(2,222,514	)		(21,582	)
	Total			(1,759,440	)		(2,222,514	)		(21,582	)
	Intangible assets subject to amortization—net			4,665,031			4,201,957			40,804
	Intangible assets not subject to amortization:
	Telephone rights			19,400			29,987			291
	Trademark			107,000			107,000			1,039
	Goodwill			5,969,951			5,969,951			57,972
	Total			6,096,351			6,106,938			59,302
	Total intangible assets		¥	10,761,382			10,308,895		$	100,106
	The weighted average amortization period for customer relationships is approximately 15.6 years. The amortization expenses for the years ended March 31, 2013 and 2014 were ¥557,559 thousand and ¥463,074  thousand ($4,497 thousand), respectively. The estimated aggregate amortization expense of intangible assets for each of the next five years is as follows:
	Year Ending March 31		Thousands of Yen			Thousands of
						U.S. Dollars
	2015		¥	397,031			3,855
	2016			388,014			3,768
	2017			380,496			3,695
	2018			365,460			3,549
	2019			355,410			3,451
	The Company recorded ¥37,000 thousand and ¥48,000 thousand of loss on impairment of the trademark right related to hi-ho in “Sales and marketing” expenses in the Company’s consolidated statement of income for the year ended March 31, 2012 and 2013, respectively. Because hi-ho recently recorded an operating loss, the Company recognized that the trademark might be impaired. The carrying value of the trademark exceeded its fair value and the impairment loss was recognized in an amount equal to the excess of the carrying amount of the trademark over the fair value of the trademark. The fair value of the trademark was calculated with the relief from royalty method. The amount of loss was included in the Network service and system integration business segment.
	The following table shows changes in the carrying amount of goodwill for the years ended March 31, 2013 and 2014, by operating segment:
			Thousands of Yen									Thousands of U.S. Dollars
			Network			ATM			Total			Network			ATM		Total
			Service and			Operation						Service and			Operation
			Systems			Business						Systems			Business
			Integration									Integration
			Business									Business
	Balance at March 31, 2012
	Goodwill		¥	5,673,064		¥	235,551		¥	5,908,615
	Accumulated impairment losses			(120,282	)		-			(120,282	)
				5,552,782			235,551			5,788,333
	Acquisition			181,618			-			181,618
	Impairment losses			-			-			-
	Balance at March 31, 2013
	Goodwill			5,854,682			235,551			6,090,233		$	56,853		$	2,287	$	59,140
	Accumulated impairment losses			(120,282	)		-			(120,282	)		(1,168	)		-		(1,168	)
				5,734,400			235,551			5,969,951			55,685			2,287		57,972
	Acquisition			-			-			-			-			-		-
	Impairment losses			-			-			-			-			-		-
	Balance at March 31, 2014
	Goodwill			5,854,682			235,551			6,090,233			56,853			2,287		59,140
	Accumulated impairment losses			(120,282	)		-			(120,282	)		(1,168	)		-		(1,168	)
			¥	5,734,400		¥	235,551		¥	5,969,951		$	55,685		$	2,287	$	57,972
	No impairment of goodwill was recognized during the years ended March 31, 2012, 2013 and 2014.
	On April 2, 2012, IIJ acquired a new subsidiary, IIJ-Exlayer and recorded goodwill of ¥181,618 thousand . The goodwill components were mainly attributable to human resources and the goodwill was included in the network service and system integration business segment.

Note_9_Leases

Note 9 - Leases	12 Months Ended
	Mar. 31, 2014
Leases [Abstract]	'
Leases of Lessee Disclosure [Text Block]	'
	9	LEASES
	The Company enters into, in the normal course of business, various leases for domestic and international backbone services, office premises, network operation centers and data communications and other equipment. Certain leases that meet one or more of the criteria set forth in the provision of ASC Topic 840, “Leases” have been classified as capital leases and the others have been classified as operating leases.
	A portion of the Company’s sales result from multi-year lease agreements, under which the Company leased some network equipment to customers. The leases are classified as sale-type leases which the Company accounts for in accordance with ASC Topic 840.
	Operating Leases— The Company has operating lease agreements with telecommunications carriers and others for the use of connectivity lines, including local access lines that customers use to connect to IIJ's network. The leases for domestic and international backbone connectivity are generally non-cancelable for a minimum one-year lease period. The Company also leases its office premises, for which refundable lease deposits are capitalized as guarantee deposits, certain office equipment under non-cancelable operating leases, and its network operation centers under non-cancelable operating leases which expire on various dates through the year 2020.
	Refundable guarantee deposits as of March 31, 2013 and 2014 consist of the following:
			Thousands of Yen				Thousands of
							U.S. Dollars
			2013		2014		2014
	Head office*		¥	1,472,311	¥	666,480	$	6,472
	Sales and subsidiaries offices			543,181		554,610		5,386
	Others			35,957		43,445		422
	Total refundable guarantee deposits		¥	2,051,449	¥	1,264,535	$	12,280
	*Guarantee deposits―current related to the present head office in amount of ¥1,462,223 thousand ($14,199 thousand) was excluded from the table above. The Company will relocate the head office on June 2014.
	Lease expenses related to backbone lines for the years ended March 31, 2012, 2013 and 2014 amounted to ¥3,370,813 thousand, ¥3,535,213 thousand and ¥3,763,803 thousand ($36,549 thousand), respectively. Lease expenses for local access lines for the years ended March 31, 2012, 2013 and 2014, which are mainly attributable to Internet connectivity services and WAN services, amounted to ¥23,101,650 thousand, ¥22,464,593 thousand and ¥22,602,364 thousand ($219,483 thousand), respectively. Other lease expenses for the years ended March 31, 2012, 2013 and 2014 amounted to ¥5,949,230 thousand, ¥5,978,985 thousand and ¥6,513,184 thousand ($63,247 thousand), respectively.
	The Company has subleased a part of its office premises. Lease expenses mentioned above have been reduced by sublease revenues totaling ¥2,394 thousand, ¥29,160 thousand and ¥ 24,082 thousand ($234 thousand) for the years ended March 31, 2012, 2013 and 2014, respectively.
	Capital Leases—The Company conducts its connectivity and other services by using data communications and other equipment leased under capital lease arrangements.
	The Company sold ATM equipment procured from third party vendors, which amounted to ¥593,715 thousand and ¥534,479 thousand ($5,190 thousand), to the leasing companies for the years ended March 31, 2013 and 2014, respectively, and concurrently entered into capital lease arrangements to lease the equipment back, which resulted in total lease payments of ¥637,548 thousand due by February 2018 and ¥585,610  thousand ($5,687 thousand) due by February 2019, related to the lease contracts made in the years ended March 31, 2013 and 2014, respectively.
	The fair values of the assets upon execution of the capital lease arrangements and accumulated depreciation amounted to ¥21,864,989 thousand and ¥13,340,942 thousand, respectively, at March 31, 2013 and ¥22,868,800 thousand ($222,070 thousand) and ¥14,795,972 thousand ($143,678 thousand), respectively, at March 31, 2014.
	Lessee Future Minimum Lease Payments—As of March 31, 2014, future lease payments under non-cancelable operating leases, including the aforementioned non-cancelable connectivity lease agreements and capital leases were as follows:
			Thousands of Yen						Thousands of U.S. Dollars
			Connectivity		Other		Capital		Connectivity		Other		Capital
			Lines		Operating		Leases		Lines		Operating		Leases
			Operating		Leases				Operating		Leases
			Leases						Leases
	Year ending March 31:
	2015		¥	1,914	¥	2,100,021	¥	3,895,597	$	19	$	20,393	$	37,828
	2016					2,792,711		2,721,272				27,119		26,425
	2017					2,796,420		1,442,649				27,155		14,009
	2018					544,892		446,161				5,291		4,333
	2019					47,999		113,880				466		1,106
	2020 and thereafter					83,002						806
	Total minimum lease payments		¥	1,914	¥	8,365,045		8,619,559	$	19	$	81,230		83,701
	Less amounts representing interest							263,211						2,556
	Present value of net minimum capital lease payments							8,356,348						81,145
	Less current portion							3,753,026						36,444
	Noncurrent portion						¥	4,603,322					$	44,701
	Sales-Type Leases—The components of the net investment in sales-type leases as of March 31, 2013 and 2014 were as follows:
			Thousands of Yen				Thousands of
							U.S. Dollars
			2013		2014		2014
	Year ending March 31:
	2015				¥	673,758	$	6,543
	2016					537,130		5,216
	2017					153,049		1,486
	2018					69,177		672
	2019					1,701		16
	Total minimum lease payments to be received*		¥	1,405,258	¥	1,434,815	$	13,933
	Estimated residual value of leased property (unguaranteed)			-		-		-
	Less unearned income			30,400		22,364		217
	Net investment in sales-type leases			1,374,858		1,412,451		13,716
	Less current portion			476,818		659,677		6,406
	Non-current net investment in sales-type leases		¥	898,040	¥	752,774	$	7,310
	*Estimated executory costs, including profit thereon, of ¥301,643 thousand and ¥268,598 thousand ($2,608 thousand) were excluded from total minimum lease payments to be received as of March 31, 2013 and 2014, respectively.

Note_10_Asset_Retirement_Oblig

Note 10 - Asset Retirement Obligations	12 Months Ended
	Mar. 31, 2014
Asset Retirement Obligation Disclosure [Abstract]	'
Asset Retirement Obligation Disclosure [Text Block]	'
	10	ASSET RETIREMENT OBLIGATIONS
	The asset retirement obligations are principally related to leasehold office premises and a data center which, at the end of the lease, the Company is contractually obligated to restore.
	The movements in asset retirement obligations for the year ended March 31, 2013 and 2014 were as follows:
			Thousands of Yen				Thousands of
							U.S. Dollars
			2013		2014		2014
	Balance at beginning of the year		¥	299,083	¥	334,585	$	3,249
	Liabilities incurred			26,620		122,157		1,186
	Liabilities settled			-		-		-
	Accretion expense			8,882		8,041		78
	Revision in estimated cash flows related to head office relocation			-		48,657		473
	Balance at end of the year		¥	334,585	¥	513,440	$	4,986

Note_11_Borrowings

Note 11 - Borrowings	12 Months Ended
	Mar. 31, 2014
Debt Disclosure [Abstract]	'
Debt Disclosure [Text Block]	'
	11	BORROWINGS
	Short-term borrowings at March 31, 2013 and 2014 consist of bank overdrafts that bear fixed rate interest. The weighted average rates at March 31, 2013 and 2014 were 0.690% and 0.600%, respectively.
	Long-term borrowings as of March 31, 2013 and 2014 consist of the following:
			Thousands of Yen						Thousands of
									U.S. Dollars
			2013			2014			2014
	Long-term installment payable at various dates through calendar 2014. Interest is payable at variable rates based on Tokyo InterBank Offered Rate (TIBOR) which were 0.250% and 0.212% as of March 31, 2013 and 2014, respectively. Weighted average interest rates were 0.962% and 0.901% at March 31, 2013 and 2014, respectively.		¥	1,990,000		¥	980,000		$	9,517
	Less current portion			(1,010,000	)	(980,000		)		( 9,517	)
	Long-term borrowings, less current portion		¥	980,000		¥	-		$	-
	Annual maturities of long-term borrowings for the years subsequent to March 31, 2014 are as follows:
			Thousands of Yen			Thousands of
						U.S. Dollars
	Year ending March 31:
	2015		¥	980,000		$	9,517
	Substantially all short-term and long-term bank borrowings are made under agreements which, as is customary in Japan, provide that under certain conditions the bank may require the borrower to provide collateral (or additional collateral) or a guarantor with respect to the borrowings and that the bank may treat any collateral, whether furnished as security for short-term or long-term loans or otherwise, as collateral for all indebtedness to such bank. Also, provisions of certain loan agreements grant certain rights of possession to the lenders in the event of default.  The Company did not provide banks with any collateral for outstanding loans as of March 31, 2014.
	The Company entered into bank overdraft agreements with certain Japanese banks for which the unused balance outstanding as of March 31, 2014 was ¥10,600,000 thousand ($102,933 thousand).

Note_12_Income_Taxes

Note 12 - Income Taxes	12 Months Ended
	Mar. 31, 2014
Income Tax Disclosure [Abstract]	'
Income Tax Disclosure [Text Block]	'
	12	INCOME TAXES
	Income taxes imposed by the national, prefectural and municipal governments of Japan resulted in a normal statutory rate of approximately 41% for the year ended March 31, 2012 and 38.3% for the years ended March 31, 2013 and 2014.
	Income from operations before income tax expense and equity in net income of equity method investees and income tax expense for the years ended March 31, 2012, 2013 and 2014 consist of the following components:
			Thousands of Yen									Thousands of
												U.S. Dollars
			2012			2013			2014			2014
	Income from operations before income tax expense and equity in net income of equity method investees:
	Domestic		¥	5,970,007		¥	7,825,846		¥	6,406,153		$	62,208
	Foreign			6,213			(68,982	)		(131,262	)		(1,275	)
	Total		¥	5,976,220		¥	7,756,864		¥	6,274,891		$	60,933
	Income taxes―current:
	Domestic		¥	2,489,350		¥	3,140,964		¥	2,453,549		$	23,825
	Foreign			422			(6,254	)		41,582			404
	Total		¥	2,489,772		¥	3,134,710		¥	2,495,131		$	24,229
	Income taxes―deferred:
	Domestic		¥	35,714		¥	(528,832	)	¥	(729,822	)	$	(7,087	)
	Foreign			-			1,704			29,996			291
	Total		¥	35,714		¥	(527,128	)	¥	(699,826	)	$	(6,796	)
	The Company adopted the consolidated tax declaration in the fiscal year ended March 31, 2009.
	Amendments to Japanese tax regulations were enacted into law on November 30, 2011. As a result, the normal Japanese statutory rate was reduced to 38.3% from the fiscal year beginning April 1, 2012 and was to be reduced to 35.9% from the fiscal year beginning April 1, 2015. On March 20, 2014, new amendments to Japanese tax regulations were enacted into law. As a result, the normal Japanese statutory rate will be reduced from 38.3% to 35.9% from the fiscal year beginning April 1, 2014. The effect of the changes in the tax rates on the balance of deferred tax assets and liabilities was a decrease of income tax expense by ¥110,381 thousand for the year ended March 31, 2012 and an increase of income tax expense by ¥106,487 thousand ($1,034 thousand) for the year ended March 31, 2014, respectively.
	The approximate effect of temporary differences and carryforwards giving rise to deferred tax balances at March 31, 2013 and 2014 were as follows:
			Thousands of Yen												Thousands of U.S. Dollars
			2013						2014						2014
			Deferred			Deferred			Deferred			Deferred			Deferred			Deferred
			Tax			Tax			Tax			Tax			Tax			Tax
			Assets			Liabilities			Assets			Liabilities			Assets			Liabilities
	Unrealized gains on available‑for‑sale securities			-		¥	290,623			-		¥	847,033			-		$	8,225
	Capital leases		¥	73,735			-		¥	106,807			-		$	1,037			-
	Accrued expenses			713,056			-			748,875			-			7,272			-
	Retirement and pension cost			758,240			-			816,558			-			7,929			-
	Allowance for doubtful accounts			66,170			-			48,885			-			475			-
	Depreciation			48,315			-			-			-			-			-
	Net loss on other investments			285,505			-			240,698			-			2,337			-
	Operating loss carryforwards			1,416,522			-			1,370,277			-			13,306			-
	Transactions in transit*			-			47,983			-			86,953			-			845
	Impairment loss on telephone rights			77,101			-			77,690			-			755			-
	Accrued enterprise tax			179,725			-			101,252			-			983			-
	Asset retirement obligation			120,116			-			184,325			-			1,790			-
	Deferred revenue			468,382			-			614,054			-			5,963			-
	Customer relationship			-			1,690,781			-			1,505,159			-			14,616
	Tax deduction of goodwill			-			528,299			-			690,499			-			6,705
	Excess of tax deductible goodwill over the reported amount of goodwill			570,356			-			316,818			-			3,077			-
	Trademark			-			38,413			-			38,413			-			373
	Investments in equity method investees			-			168,061			-			233,550			-			2,268
	Other			237,761			159,753			217,213			166,346			2,109			1,615
	Total			5,014,984			2,923,913			4,843,452			3,567,953			47,033			34,647
	Valuation allowance			(1,361,807	)		-			(428,184	)		-			(4,158	)		-
	Total		¥	3,653,177		¥	2,923,913		¥	4,415,268		¥	3,567,953		$	42,875		$	34,647
	*This item arises from transactions between IIJ and foreign subsidiaries, which were recorded in the different periods as a result of the difference in each company’s fiscal year-end.
	As of March 31, 2013 and 2014, the valuation allowance for deferred tax assets related principally to operating loss carryforwards, at amounts which are not considered more likely than not to be realized. The net changes in the valuation allowance for deferred tax assets were a decrease of ¥136,689 thousand, ¥647,079 thousand and ¥933,623 thousand ($9,066 thousand) for the years ended March 31, 2012, 2013 and 2014, respectively.
	Undistributed earnings of foreign subsidiaries that are deemed to be permanently invested amounted to ¥403,040 thousand ($3,914 thousand) as of March 31, 2014. It is not practicable to calculate the unrecognized deferred tax liability on such undistributed earnings.
	As of March 31, 2014, certain subsidiaries had tax operating loss carryforwards as follows.
			Thousands of Yen
	Year Ending		Enterprise Tax			Inhabitant Tax			Others
	31-Mar		Subject to			Subject to
			Consolidation Tax			Consolidation Tax
			Filing			Filing
	2015			-			-			-
	2016			-			-			-
	2017			-			-			-
	2018		¥	38,120		¥	10,762		¥	411,351
	2019 and thereafter			221,664			62,745			3,339,609
	Total		¥	259,784		¥	73,507		¥	3,750,960
		Thousands of U.S. Dollars
Year Ending		Enterprise Tax			Inhabitant Tax			Others
31-Mar		Subject to			Subject to
		Consolidation Tax			Consolidation Tax
		Filing			Filing
2015			-			-			-
2016			-			-			-
2017			-			-			-
2018		$	370		$	105		$	3,994
2019 and thereafter			2,153			609			32,430
Total		$	2,523		$	714		$	36,424
“Others” were loss carryforwards of subsidiaries not subject to consolidation tax filing, which were composed of ¥2,310,209 thousand ($22,434 thousand) in Japan, ¥1,017,046 thousand ($9,876 thousand) in the United States of America, and ¥423,705 thousand ($4,114 thousand) in other countries.
These loss carryforwards are available to offset future taxable income, and will expire in the period ending March 31, 2022 in Japan and December 31, 2033 in the United States of America. The loss carryforwards in other countries will expire in the period ending December 31, 2018 or have an indefinite carryforward period.
A reconciliation between the amount of reported income taxes and the amount of income taxes computed using the normal statutory rate for each of the three years in the period ended March 31, 2014 is as follows:
		Thousands of Yen									Thousands of
											U.S. Dollars
		2012			2013			2014			2014
Amount computed by using normal Japanese statutory tax rate		¥	2,450,250		¥	2,970,879		¥	2,403,283		$	23,337
Increase (decrease) in taxes resulting from:
Expenses not deductible for tax purpose			81,115			89,012			102,634			997
Inhabitant tax―per capita			34,415			35,809			37,122			360
Expiration of operating loss carryforward			176,829			-			-			-
Change in valuation allowance			(107,171	)		(666,973	)		(957,182	)		(9,295	)
Tax effects on investments in equity method investees			-			168,061			65,489			636
Enterprise tax―not based on income			68,960			77,868			82,191			798
Tax rate change			(110,381	)		-			106,487			1,034
Other—net			(68,531	)		(67,074	)		(44,719	)		(434	)
Income tax expense as reported		¥	2,525,486		¥	2,607,582		¥	1,795,305		$	17,433
There was no amount of unrecognized tax benefit for the year ended March 31, 2013 and 2014. The Company does not reasonably expect that the unrecognized tax benefit will change significantly within the next twelve months.
The Company has open tax years subject to examination by major tax jurisdictions from the year ended March 31, 2013 in Japan and from the year ended December 31, 2006 in the United States of America.

Note_13_Retirement_and_Pension

Note 13 - Retirement and Pension Plans	12 Months Ended
	Mar. 31, 2014
Compensation and Retirement Disclosure [Abstract]	'
Pension and Other Postretirement Benefits Disclosure [Text Block]	'
	13	RETIREMENT AND PENSION PLANS
	IIJ and certain subsidiaries had unfunded severance benefit, noncontributory defined benefit pension and defined contribution plans which together covered substantially all of their employees who were not directors. The defined benefit pension plan is operated under the Defined Benefit Corporate Pension Law.
	The following information regarding net periodic pension cost and accrued pension cost also includes the unfunded severance benefit plans. Under the severance and defined benefit pension plans, all of IIJ and IIJ-Global’s employees are entitled, upon retirement with 20 years or more service, to a 10-year period of annuity payments from age 60 (or lump-sum severance indemnities) based on the rate of pay at the time of retirement, length of service and certain other factors. IIJ and IIJ-Global's employees who do not meet these conditions are entitled to lump-sum severance indemnities.
	Net periodic pension cost for the years ended March 31, 2012, 2013 and 2014 included the following components:
			Thousands of Yen									Thousands of
												U.S. Dollars
			2012			2013			2014			2014
	Service cost		¥	467,583		¥	479,158		¥	542,584		$	5,269
	Interest cost			48,335			46,975			45,418			441
	Expected return on plan assets			(27,086	)		(29,796	)		(48,303	)		(470	)
	Amortization of transition obligation			369			369			369			4
	Other			(12,632	)		-			-			-
	Net periodic pension cost		¥	476,569		¥	496,706		¥	540,068		$	5,244
	Other changes in plan assets and benefit obligations recognized in other comprehensive income for the years ended March 31, 2012, 2013 and 2014 are as follows:
			Thousands of Yen									Thousands of
												U.S. Dollars
			2012			2013			2014			2014
	Net actuarial loss (gain)		¥	39,083		¥	92,808		¥	(63,775	)	$	(619	)
	Amortization of transition obligation in net periodic pension cost			(369	)		(369	)		(369	)		(4	)
	Other			12,632			-			-			-
	Amounts recognized in other comprehensive income (loss)		¥	51,346		¥	92,439		¥	(64,144	)	$	(623	)
	Total net periodic pension cost and amounts recognized in other comprehensive income		¥	527,915		¥	589,145		¥	475,924		$	4,621
	The change in benefit obligation and plan assets for the years ended March 31, 2013 and 2014 and the amounts recognized in the consolidated balance sheets as of March 31, 2013 and 2014 are as follows:
			Thousands of Yen						Thousands of
									U.S. Dollars
			2013			2014			2014
	Change in benefit obligation:
	Benefit obligation at beginning of year		¥	3,196,857		¥	3,855,332		$	37,438
	Service cost			479,158			542,584			5,269
	Interest cost			46,975			45,418			441
	Actuarial loss			209,406			17,098			166
	Benefit paid			(77,064	)		(33,834	)		(329	)
	Benefit obligation at end of year			3,855,332			4,426,598			42,985
	Change in plan assets:
	Fair value of plan assets at beginning of year			1,655,373			2,012,611			19,544
	Actual return on plan assets			146,394			129,176			1,254
	Employer contribution			257,288			296,631			2,880
	Benefits paid			(46,444	)		(13,919	)		(135	)
	Fair value of plan assets at end of year			2,012,611			2,424,499			23,543
	Funded status at end of year		¥	(1,842,721	)	¥	(2,002,099	)	$	(19,442	)
	Amounts recognized in the consolidated balance sheets as of March 31, 2013 and 2014 consist of:
			Thousands of Yen						Thousands of
									U.S. Dollars
			2013			2014			2014
	Accrued retirement and pension costs―noncurrent		¥	(1,842,721	)	¥	(2,002,099	)	$	(19,442	)
	Net amount recognized		¥	(1,842,721	)	¥	(2,002,099	)	$	(19,442	)
	The accumulated benefit obligation for the Company’s defined benefit pension plans as of March 31, 2013 and 2014 was ¥2,444,643 thousand and ¥2,765,988 thousand ($26,859 thousand), respectively.
	The aggregate projected benefit obligation and aggregate fair value of plan assets for plans with projected benefit obligations in excess of plan assets were ¥3,855,332 thousand and ¥2,012,611 thousand at March 31, 2013 and ¥4,426,598 thousand ($42,985 thousand) and ¥2,424,499 thousand ($23,543 thousand) at March 31, 2014, respectively. The aggregate accumulated benefit obligations of plans with no plan assets were ¥70,425 thousand and ¥79,449 thousand ($771 thousand) at March 31, 2013 and 2014, respectively.
	Amounts recognized in accumulated other comprehensive income at March 31, 2013 and 2014 consist of:
			Thousands of Yen						Thousands of
									U.S. Dollars
			2013			2014			2014
	Net actuarial loss		¥	305,049		¥	241,275		$	2,343
	Obligation at transition			1,104			734			7
	Total		¥	306,153		¥	242,009		$	2,350
	The unrecognized net loss and the unrecognized net obligation at the date of initial application are being amortized over 14 years and 21 years, respectively.
	The estimated net actuarial loss and obligation at transition for the defined benefit pension plans that will be amortized from accumulated other comprehensive income into net periodic pension cost in the fiscal year ending March 31, 2015 are zero and ¥369 thousand ($4 thousand), respectively.
			Benefit						Net Periodic Costs
			Obligations
			2013			2014			2012			2013			2014
	Discount rate			1.2	%		1.7	%		1.8	%		1.5	%		1.2	%
	Expected long-term rate of return on plan assets									1.9			1.8			2.4
	Rate of increase in compensation			3.3			3.2			3.4			3.3			3.3
The Company sets the discount rate assumption annually at March 31 based on high-quality fixed income securities reflecting the estimated timing of benefit payments.
The basis for determining the long-term rate of returns is a combination of historical returns and prospective return assumptions derived from pension trust funds’ managing company.
The following benefit payments, which reflect expected future service, as appropriate, are expected to be paid.
Years Ending		Thousands of Yen			Thousands of
31-Mar					U.S. Dollars
2015		¥	64,015		$	622
2016			75,530			734
2017			99,316			964
2018			123,816			1,202
2019			134,463			1,306
2020－2024			1,279,018			12,420
Total		¥	1,776,158		$	17,248
The Company expects to contribute ¥296,630 thousand ($2,880 thousand) to its defined benefit pension plan in the year ending March 31, 2015.
The Company’s defined contribution plan, which was established on April 1, 2009, covers substantially all its employees. The Company contributes monthly 1.6% of its employees’ base salaries to the plan. No employee contributions to the plan are allowed. Contributions to the plan were ¥109,224 thousand, ¥114,450 thousand and ¥125,195 thousand ($1,216 thousand) for the years ended March 31, 2012, 2013 and 2014, respectively.
The Company's funding policies with respect to the noncontributory plan are generally to contribute amounts considered tax deductible under applicable income tax regulations. Plan assets including life insurance pooled investment portfolios consist of Japanese government bonds, other debt securities and marketable equity securities.
Life insurance pooled investment portfolios are managed by an insurance company and guarantee a minimum rate of return.
The Company’s investment strategy for the plan assets is to manage the assets in order to pay retirement benefits to plan participants from the Company over the life of the plans.
This is accomplished by identifying and managing the exposure to various market risks, diversifying investments in various asset classes based on portfolio determined by the insurance company in order to maximize long-term rate of return, while considering the liquidity needs of the plans.
The plan is permitted to use derivative instruments only for the purpose of hedging. Both margin trading and real-estate investment are prohibited in principle.
The Company mitigates the credit risk of investments by establishing guidelines with the insurance company. These guidelines are monitored periodically by the Company for compliance.
The projected allocation of the plan assets managed by the insurance company is developed in consideration of the expected long-term investment returns for each category of the plan assets. Approximately 63.0%, 35.0%, and 2.0% of the plan assets excluding pooled investment portfolios will be allocated to debt securities, equity securities and other financial instruments, respectively, to moderate the level of volatility in pension plan asset returns and reduce risks. Fifty percent of the employer’s contribution to the plan during the year ending March 31, 2015 will be allocated to life insurance pooled investment portfolios and other 50% will be allocated to the aforementioned investments.
The following table summarizes the basis used to measure the Company’s pension plan assets at fair value:
Level 1―Inputs are quoted prices in active markets for identical assets or liabilities.
Level 2―Inputs are quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable, and inputs that are derived principally from or corroborated by observable market data by correlation or other means.
Level 3―Inputs are derived from valuation techniques in which one or more significant inputs or value drivers are unobservable, which reflect the reporting entity’s own assumptions about the assumptions that market participants would use in establishing a price.
Basis of Fair Value Measurement of Pension Plan Assets at March 31, 2013		Thousands of Yen
		Level 1			Level 2			Level 3			Total
Equity securities:
Japanese equity		¥	302,533			-			-		¥	302,533
U.S. equity			72,760			-			-			72,760
Other equity―developed countries			51,220			-			-			51,220
Total equity securities			426,513			-			-			426,513
Debt securities:
Japanese government and municipalities			-		¥	477,430			-			477,430
Japanese corporate bonds―investment grade			-			59,533			-			59,533
U.S. government			-			74,294			-			74,294
Other government―developed countries			-			103,471			-			103,471
Residential mortgage-backed			-			26,252			-			26,252
Total debt securities			-			740,980			-			740,980
Other financial instruments*			-			800,968			-			800,968
Cash			44,150			-			-			44,150
Total assets at fair value		¥	470,663		¥	1,541,948			-		¥	2,012,611
Basis of Fair Value Measurement of Pension Plan Assets at March 31, 2014		Thousands of Yen
		Level 1			Level 2			Level 3			Total
Equity securities:
Japanese equity		¥	348,758			-			-		¥	348,758
U.S. equity			89,304			-			-			89,304
Other equity― developed countries			61,498			-			-			61,498
Total equity securities			499,560			-			-			499,560
Debt securities:
Japanese government and municipalities			-		¥	486,308			-			486,308
Japanese corporate bonds― investment grade			-			164,037			-			164,037
U.S. government			-			65,339			-			65,339
Other government― developed countries			-			151,824			-			151,824
Residential mortgage-backed			-			19,337			-			19,337
Total debt securities			-			886,845			-			886,845
Other financial instruments*			-			950,011			-			950,011
Cash			88,083			-			-			88,083
Total assets at fair value		¥	587,643		¥	1,836,856			-		¥	2,424,499
Basis of Fair Value Measurement of Pension Plan Assets at March 31, 2014		Thousands of U.S. Dollars
		Level 1			Level 2			Level 3			Total
Equity securities:
Japanese equity		$	3,387			-			-		$	3,387
U.S. equity			867			-			-			867
Other equity―developed countries			597			-			-			597
Total equity securities			4,851			-			-			4,851
Debt securities:
Japanese government and municipalities			-		$	4,722			-			4,722
Japanese corporate bonds―investment grade			-			1,593			-			1,593
U.S. government			-			635			-			635
Other government―developed countries			-			1,474			-			1,474
Residential mortgage-backed			-			188			-			188
Total debt securities			-			8,612			-			8,612
Other financial instruments*			-			9,225			-			9,225
Cash			855			-			-			855
Total assets at fair value		$	5,706		$	17,837			-		$	23,543
* Other financial instruments are life insurance pooled investment portfolios.
Pension plan assets classified as Level 1 are comprised principally of equity securities, which are valued using an unadjusted quoted market price in active markets with sufficient volume and frequency of transactions.
Pension plan assets classified as Level 2 are comprised principally of government bonds, corporate bonds and life insurance pooled investment portfolios which are valued based on quoted prices obtained from a well-established third-party. The bonds are traded in less active markets and the fair values are based on the price a dealer would pay for the bonds.
IIJ and a certain subsidiary participated in a contributory multi-employer pension plan, the Japan Computer Information Service Employee's Pension Fund (the "Multi-Employer Plan"), which covered substantially all of their employees.
As stipulated by the Japanese Welfare Pension Insurance Law, the Multi-Employer Plan is composed of a substitutional portion of Japanese Pension Insurance and a multi-employers' portion of a contributory defined benefit pension plan. The benefits for the substitutional portion are based on a standard remuneration schedule under the Welfare Pension Insurance Law and the length of participation. The multi-employer portion of the benefits is based on the employee's length of service. However, assets contributed by an employer including IIJ are not segregated in a separate account or restricted to provide benefits only to employees of that employer. The net pension cost under the Multi-Employer Plan is recognized when contributions become due.
Contributions due and paid during the years ended March 31, 2012, 2013 and 2014 under the Multi-Employer Plan, including its substitutional portion, amounted to ¥214,987 thousand, ¥244,666 thousand and ¥265,470 thousand ($2,578 thousand), respectively. The Company’s contribution did not represent more than 5% of total contributions to the plan during the years ended March 31, 2012, 2013 and 2014.
The plan is not subject to a funding improvement and is more than 80% funded as of March 31, 2013. The total plan assets are ¥626,988,803 thousand ($6,088,452 thousand) as of March 31, 2014. It was difficult to obtain other additional information for the plan for the year ended March 31, 2014.
The amount of retirement benefits for retiring directors and company auditors must be approved by the shareholders.
IIJ has a retirement plan for full-time company auditors. The Company recorded a liability for retirement benefit for company auditors of ¥3,690 thousand and ¥3,520 thousand ($34 thousand), which would be required if they were all to retire at March 31, 2013 and 2014, respectively.
IIJ had a retirement benefit plan for full-time directors, which was abolished in June 2011. The allowance for retirement benefit amounted to ¥255,330 thousand ($2,479 thousand) in consideration of their services made up to the date of abolition of the plan, and this amount will be reserved until each director’s retirement date. IIJ’s subsidiary also has a retirement benefit plan for full-time directors. The Company recorded a liability for retirement benefit for full-time directors of ¥265,674 thousand and ¥268,921 thousand ($2,611 thousand), which would be required if they were all to retire at March 31, 2013 and 2014, respectively.
The retirement benefits paid to retired company auditor was ¥2,010 thousand ($20 thousand) for the year ended March 31, 2014.

Note_14_Shareholders_Equity

Note 14 - Shareholders' Equity	12 Months Ended
	Mar. 31, 2014
Stockholders' Equity Note [Abstract]	'
Stockholders' Equity Note Disclosure [Text Block]	'
	14	SHAREHOLDERS' EQUITY
	Japanese companies are subject to the Companies Act of Japan (the “Companies Act”).  The significant provisions in the Companies Act that affect financial and accounting matters are summarized below:
	Dividends
	Under the Companies Act, companies can pay dividends at any time during the fiscal year in addition to the year-end dividend upon resolution at the shareholders meeting.  For companies that meet certain criteria such as: (1) having a Board of Directors, (2) having independent auditors, (3) having a Board of Company Auditors, and (4) the term of service of the directors is prescribed as one year rather than two years of normal term by its articles of incorporation, the Board of Directors may declare dividends (except for dividends in kind) at any time during the fiscal year if the company has prescribed so in its articles of incorporation. However, the Company cannot do so because it does not meet criteria (4) above. The Companies Act permits companies to distribute dividends-in-kind (non-cash assets) to shareholders subject to a certain limitation and additional requirements. Semiannual interim dividends may also be paid once a year upon resolution by the Board of Directors if the articles of incorporation of the company so stipulate. The Companies Act provides certain limitations on the amounts available for dividends or the purchase of treasury stock. The limitation is defined as the amount available for distribution to the shareholders, but the amount of net assets after dividends must be maintained at no less than ¥3 million.
	At the 14th Ordinary General Shareholders Meeting held on June 28, 2006, IIJ’s shareholders approved the reductions of additional paid-in capital of ¥21,980,395 thousand and common stock of ¥2,539,222 thousand to eliminate the accumulated deficit for the purpose of reporting under the Companies Act in its non-consolidated financial statements. The effective date was August 4, 2006.
	Increases / decreases and transfer of common stock, reserve and surplus
	The Companies Act requires that an amount equal to 10% of dividends must be appropriated as legal reserve (a component of retained earnings) or as additional paid-in capital (a component of capital surplus) depending on the equity account charged upon the payment of such dividends until the total of aggregate amount of legal reserve and additional paid-in capital equals 25% of common stock. Under the Companies Act, the total amount of additional paid-in capital and legal reserve may be reversed without limitation. The Companies Act also provides that common stock, legal reserve, additional paid-in capital, and other capital surplus and retained earnings can be transferred among the accounts under certain conditions upon resolution of shareholders.
	Treasury stock and treasury stock acquisition rights
	The Companies Act also provides for companies to purchase treasury stock and dispose of such treasury stock by resolution of the Board of Directors. The amount of treasury stock purchased cannot exceed the amount available for distribution to the shareholders which is determined by specific formula.
	The Companies Act also provides that companies can purchase both treasury stock acquisition rights and treasury stock.
	The amount of retained earnings available for dividends under the Companies Act is based on the amount of retained earnings recorded in IIJ’s general books of account prepared using accepted Japanese accounting practices. The adjustments included in the accompanying consolidated financial statements for U.S. GAAP purposes but not recorded in the general books of account have no effect on the determination of retained earnings available for dividends under the Companies Act. Retained earnings shown in IIJ’s general books of account amounted to ¥21,076,781 thousand ($204,669 thousand) at March 31, 2014.
	On June 28, 2011, IIJ’s shareholders approved the payment of a cash dividend to shareholders of record at March 31, 2011 of ¥7.5 per share or in the aggregate amount of ¥304,026 thousand.
	On November 8, 2011, the Board of Directors of IIJ resolved the payment of a cash dividend to shareholders of record at September 30, 2011 of ¥7.5 per share or in the aggregate amount of ¥304,026 thousand.
	On June 27, 2012, IIJ’s shareholders approved the payment of a cash dividend to shareholders of record at March 31, 2012 of ¥8.75 per share or in the aggregate amount of ¥354,697 thousand.
	On November 8, 2012, the Board of Directors of IIJ resolved the payment of a cash dividend to shareholders of record at September 30, 2012 of ¥8.75 per share or in the aggregate amount of ¥354,697 thousand.
	The forementioned cash dividends per share are retroactively adjusted to reflect a 1:200 stock split conducted on October 1, 2012.
	In July 2013, IIJ completed a public offering of 4,700,000 new shares of common stock by a firm-commitment underwriting at an issue price of ¥3,346 ($32.49) (an amount paid of ¥3,208 ($31.15)) per share on the Tokyo Stock Exchange. In August 2013, IIJ issued 700,000 new shares of common stock by way of Third-Party Allotment at an amount paid of ¥3,208 ($31.15) per share. Stock issuance costs of ¥51,996 thousand ($505 thousand) (net of tax) were deducted from additional paid-in-capital. The total of net proceeds to IIJ from the public offering and the third-party allotment, after deducting stock issuance costs, were ¥17,271,204 thousand ($167,714 thousand).
	On June 26, 2013, IIJ’s shareholders approved the payment of a cash dividend to shareholders of record at March 31, 2013 of ¥10 per share or in the aggregate amount of ¥405,368 thousand ($3,936 thousand).
	On November 8, 2013, the Board of Directors of IIJ resolved the payment of a cash dividend to shareholders of record at September 30, 2013 of ¥11 per share or in the aggregate amount of ¥505,329 thousand ($4,908 thousand).
	Stock Option Plans
	On May 26, 2011, IIJ’s board of directors resolved to introduce stock compensation–type stock options for executive officers of IIJ. On June 28, 2011, IIJ’s ordinary general meeting of shareholders approved the introduction of stock compensation-type stock options for directors of IIJ. Stock compensation-type stock options, which are stock acquisition rights entitling holders to acquire shares upon exercise, at an exercise price of one yen per share, were allocated to directors and executive officers as a substitute for the retirement allowance plan for them and to further promote their motivation and incentives to contribute to the enhancement of the mid- to long-term continuous business performance and corporate value.
	The stock acquisition rights become exercisable after a service period of one year and are exercisable up to 29 years from the date of vesting. The stock acquisition rights may be exercised only within 10 days from the day immediately following the day on which the person loses his or her position as either a director or an executive officer. On July 14, 2011, IIJ granted 138 stock options to directors and executive officers. The fair value per option at the date of grant was ¥259,344.
	On July 13, 2012, IIJ granted 130 stock options which were the same type of options granted in 2011 to directors and executive officers. The fair value per option at the date of grant was ¥318,562.
	On July 11, 2013, IIJ granted 89 stock options which were the same type of options granted in 2012 to directors and executive officers. The fair value per option at the date of grant was ¥647,000 ($6,283).
	The fair value of stock acquisition rights used to recognize compensation expense for the fiscal years ended March 31, 2012, 2013 and 2014 were estimated using the Black-Scholes option-pricing model with the following assumptions:
			2012			2013			2014
	Assumptions:
	Risk-free interest rate			1.614	%		1.298	%		1.314	%
	Expected lives (years)			15			15			15
	Expected volatility			59.892	%		57.02	%		55.861	%
	Expected dividends			0.924	%		0.893	%		0.535	%
	A summary of the activities for the stock acquisition rights plan for the years ended March 31, 2013 and 2014 is as follows:
									Yen			Years		Thousands		Thousands
														of Yen		of U.S.
																Dollars
			Number			Number			Exercise			Remaining		Total		Total
			of Options			of Shares			Price			Life		Intrinsic		Intrinsic
														Value		Value
	Unexercised options outstanding—March 31, 2012			138			27,600			1
	Granted			130			26,000			1
	Exercised			-			-			-
	Forfeited or expired			-			-			-
	Unexercised options outstanding—March 31, 2013			268			53,600			1
	Granted			89			17,800			1
	Exercised			11			2,200			1
	Forfeited or expired			-			-			-
	Unexercised options outstanding—March 31, 2014			346			69,200			1
	Exercisable options—March 31, 2014			257			51,400			1			27.79	¥	127,523	$	1,238
	Expected to vest after July 10, 2014			89			17,800			1			29.28	¥	44,162	$	429
	*Due to the effect of the stock split conducted on October 1, 2012, grantees of options can purchase 200 shares by exercising one option.
	The Company recognized stock compensation cost on a straight-line basis over the requisite service period.
	The Company recognized ¥26,843 thousand, ¥40,007 thousand and ¥53,542 thousand ($520 thousand) as stock compensation cost for the fiscal years ended March 31,2012, 2013 and 2014, respectively. The unrecognized expense of ¥14,396 thousand ($140 thousand) is expected to be recognized over next 3 months.
	During the fiscal year ended March 31, 2012, IIJ acquired noncontrolling interests of GDX for ¥5 thousand, and GDX became a wholly owned subsidiary of IIJ. IIJ also acquired additional shares issued by Trust Networks for ¥300,000 thousand during the fiscal year ended March 31, 2012. IIJ had owned controlling interests of both subsidiaries, and the decrease in IIJ’s shareholders ownership interest due to the acquisitions of the additional shares were accounted for as capital transactions in accordance with ASC Topic 810-10-65, “Consolidation―Noncontrolling Interests in Consolidated Financial Statements―an amendment of ARB No. 51.”
	IIJ absorbed IIJ-Exlayer on January 1, 2014 with the allotment of 104 shares of IIJ’s treasury stock to the shareholder of IIJ-Exlayer.
	Net income attributable to IIJ’s shareholders and transfers (to) from the noncontrolling interests
	The following schedule represents the effects of changes in IIJ’s ownership interest in its subsidiaries in the Company’s shareholder’s equity for the years ended March 31, 2012, 2013 and 2014.
			Thousands of Yen									Thousands of
												U.S. Dollars
			2012			2013			2014			2014
	Net income attributable to IIJ		¥	3,640,963		¥	5,300,654		¥	4,442,237		$	43,137
	Transfers (to) from the noncontrolling interests
	Decrease in additional paid-in capital for purchase of GDX common shares			(85,437	)		-			-			-
	Increase in additional paid-in capital for acquisition of noncontrolling interest of IIJ-Exlayer			-			-			99			1
Net transfers (to) from noncontrolling interest			(85,437	)		-			99			1
Change from net income attributable to IIJ and transfers (to) from noncontrolling interests		¥	3,555,526		¥	5,300,654		¥	4,442,336		$	43,138

Note_15_Other_Comprehensive_In

Note 15 - Other Comprehensive Income (Loss)	12 Months Ended
	Mar. 31, 2014
Disclosure Text Block [Abstract]	'
Comprehensive Income (Loss) Note [Text Block]	'
	15	OTHER COMPREHENSIVE INCOME (LOSS)
	Tax effects allocated to each component of other comprehensive income (loss) and reclassification adjustments for the years ended March 31, 2012, 2013 and 2014 are as follows:
			Thousands of Yen
			Before Tax			Tax (Expense)			Net of Tax
			Amount			Benefit			Amount
	Year ended March 31, 2012:
	Foreign currency translation adjustments		¥	(9,539	)		-		¥	(9,539	)
	Unrealized holding gain (loss) on securities:
	Amount arising during the period			56,384		¥	(20,242	)		36,142
	Less:  Reclassification adjustments for losses included in net income			91,064			(37,336	)		53,728
	Other			-			12,875			12,875
	Net unrealized holding gain (loss) during the period			147,448			(44,703	)		102,745
	Defined benefit pension plans:
	Amount arising during the period			(39,083	)		14,030			(25,053	)
	Less: Reclassification adjustments for gains included in net income			(12,263	)		5,711			(6,552	)
	Net defined benefit pension plans			(51,346	)		19,741			(31,605	)
	Other comprehensive income (loss)		¥	86,563		¥	(24,962	)	¥	61,601
	Year ended March 31, 2013:
	Foreign currency translation adjustments		¥	90,014			-		¥	90,014
	Unrealized holding gain (loss) on securities:
	Amount arising during the period			380,637		¥	(136,649	)		243,988
	Less:  Reclassification adjustments for losses included in net income			19,788			(7,579	)		12,209
	Other			-			324			324
	Net unrealized holding gain (loss) during the period			400,425			(143,904	)		256,521
	Defined benefit pension plans:
	Amount arising during the period			(92,808	)		33,319			(59,489	)
	Less: Reclassification adjustments for losses included in net income			369			(132	)		237
	Net defined benefit pension plans			(92,439	)		33,187			(59,252	)
	Other comprehensive income (loss)		¥	398,000		¥	(110,717	)	¥	287,283
			Thousands of Yen
			Before Tax			Tax (Expense)			Net of Tax
			Amount			Benefit			Amount
	Year ended March 31, 2014:
	Foreign currency translation adjustments		¥	419,557			-		¥	419,557
	Unrealized holding gain (loss) on securities:
	Amount arising during the period			1,656,759		¥	(594,776	)		1,061,983
	Less: Reclassification adjustments for gains included in net income			(107,655	)		41,232			(66,423	)
	Other			-			(7,421	)		(7,421	)
	Net unrealized holding gain (loss) during the period			1,549,104			(560,965	)		988,139
	Defined benefit pension plans:
	Amount arising during the period			63,775			(22,896	)		40,879
	Less: Reclassification adjustments for losses included in net income			369			(133	)		236
	Net defined benefit pension plans			64,144			(23,029	)		41,115
	Other comprehensive income (loss)		¥	2,032,805		¥	(583,994	)	¥	1,448,811
			Thousands of U.S. Dollars
			Before Tax			Tax (Expense)			Net of Tax
			Amount			Benefit			Amount
	Year ended March 31, 2014:
	Foreign currency translation adjustments		$	4,074			-		$	4,074
	Unrealized holding gain (loss) on securities:
	Amount arising during the period			16,088		$	(5,776	)		10,312
	Less: Reclassification adjustments for gains included in net income			(1,045	)		400			(645	)
	Other			-			(71	)		(71	)
	Net unrealized holding gain (loss) during the period			15,043			(5,447	)		9,596
	Defined benefit pension plans:
	Amount arising during the period			619			(222	)		397
	Less: Reclassification adjustments for gains included in net income			4			(2	)		2
	Net defined benefit pension plans			623			(224	)		399
	Other comprehensive income (loss)		$	19,740		$	(5,671	)	$	14,069
	The changes in accumulated other comprehensive income (loss) by component for the years ended March 31, 2014 are as follows:
			Thousands of Yen
			Unrealized holding			Defined benefit			Foreign currency			Total
gain on securities			pension plans			translation
						adjustments
Year ended March 31, 2013:		¥	495,217		¥	(187,318	)	¥	(44,129	)	¥	263,770
Other comprehensive income before reclassifications			1,054,562			40,879			419,701			1,515,142
Amounts reclassified out of accumulated other comprehensive income			(66,423	)		236			―			(66,187	)
Other comprehensive income			988,139			41,115			419,701			1,448,955
Other			―			―			61			61
Year ended March 31, 2014:		¥	1,483,356		¥	(146,203	)	¥	375,633		¥	1,712,786
		Thousands of U.S. Dollars
		Unrealized holding			Defined benefit			Foreign currency			Total
		gain on securities			pension plans			translation
								adjustments
Year ended March 31, 2013:		$	4,809		$	(1,820	)	$	(428	)	$	2,561
Other comprehensive income before reclassifications			10,241			397			4,075			14,713
Amounts reclassified out of accumulated other comprehensive income			(645	)		2			―			(643	)
Other comprehensive income			9,596			399			4,075			14,070
Other			―			―			1			1
Year ended March 31, 2014:		$	14,405		$	(1,421	)	$	3,648		$	16,632
The amounts reclassified from accumulated other comprehensive income to the consolidated statements of income, with presentation location, for the year ended March 31, 2014, are as follows:
		Thousands of Yen			Thousands of
					U.S. Dollars
		2014			2014
Comprehensive income components:								Location
Unrealized holding gain on securities		¥	107,655		$	1,045		Net gain on sales of other investments
			(41,232	)		(400	)	Income tax expense
			66,423			645		Net income
Defined benefit pension plans			(369	)		(4	)	Net periodic pension costs (Note 13)
			133			2		Income tax expense
			(236	)		(2	)	Net income
Total amount reclassified		¥	66,187		$	643

Note_16_Basic_and_Diluted_Net_

Note 16 - Basic and Diluted Net Income Per Common Share	12 Months Ended
	Mar. 31, 2014
Earnings Per Share [Abstract]	'
Earnings Per Share [Text Block]	'
	16	BASIC AND DILUTED NET INCOME PER COMMON SHARE
	Basic and diluted net income attributable to Internet Initiative Japan Inc. per common share computation for three years ended March 31, 2012, 2013 and 2014 is as follows:
			Thousands of Yen						Thousands of
									U.S. Dollars
			2012		2013		2014		2014
	Numerator―
	Net income attributable to Internet Initiative Japan Inc.―basic and diluted		¥	3,640,963	¥	5,300,654	¥	4,442,237	$	43,137
			Number of Shares
			2012		2013		2014
	Denominator:
	Weighted-average common shares outstanding―basic			40,536,800		40,536,800		44,306,680
	Dilutive effect of stock options			19,600		35,800		54,403
	Weighted-average common shares outstanding―diluted			40,556,400		40,572,600		44,361,083
			Yen						U.S. Dollars
			2012		2013		2014		2014
	Basic net income attributable to Internet Initiative Japan Inc. per common share		¥	89.82	¥	130.76	¥	100.26	$	0.97
	Diluted net income attributable to Internet Initiative Japan Inc. per common share		¥	89.78	¥	130.65	¥	100.14	$	0.97
	Note: Figures shown above are retroactively adjusted to reflect a 1:200 stock split conducted on October 1, 2012.

Note_17_Commitments_And_Contin

Note 17 - Commitments And Contingent Liabilities	12 Months Ended
	Mar. 31, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Commitments and Contingencies Disclosure [Text Block]	'
	17	COMMITMENTS AND CONTINGENT LIABILITIES
	The Company is involved in litigation and claims arising in the ordinary course of business. In evaluating the matter on an ongoing basis, the Company takes into account amounts already accrued on the balance sheet.  The Company believes that an exposure to loss does not exist in excess of the amount accrued and the negative adverse outcome of such litigation and claims would not have a significant impact on the consolidated financial position or results of operations.
	On September 1, 2010, IIJ-Global entered into a Solutions Engagement Agreement with IBM Japan Ltd,   IIJ-Global’s largest sales partner. This agreement, which establishes the basis for a procurement relationship between IIJ-Global and IBM Japan, contains indemnification for IIJ-Global to perform services, functions, responsibilities and others in a way that were being performed by AT&T Japan.
	In May 2006, January 2007 and January 2008, IIJ made agreements (three agreements in total) for investing in funds which invest in mainly unlisted stocks with an investment advisory company. IIJ committed to provide up to $5 million for each fund ($15 million in total) upon the request of the fund until June 30, 2020. IIJ has provided a total of $12.6 million to them as of March 31, 2014. The amounts invested in their funds were recorded as other investments in the Company’s consolidated balance sheets.
	In April 2013, IIJ made an agreement for investing in a corporation reconstruction fund with an investment advisory company. IIJ committed to provide up to ¥100 million upon the request of the fund until April 23, 2018. IIJ has provided a total of ¥19 million to the fund as of March 31, 2014. The amounts invested in the fund were recorded as other investments in the Company’s consolidated balance sheets.

Note_18_Financial_Instruments

Note 18 - Financial Instruments	12 Months Ended
	Mar. 31, 2014
Disclosure Text Block Supplement [Abstract]	'
Financial Instruments Disclosure [Text Block]	'
	18	FINANCIAL INSTRUMENTS
	Fair Value—In the normal course of business, the Company invests in financial assets. To estimate the fair value of those financial assets, the Company used quoted market prices to the extent that they are available. Where a quoted market price is not available, the Company estimates fair value using primarily the discounted cash flow method. For certain financial assets and liabilities, such as trade receivables and trade payables, which are expected to be collected and settled within one year, the Company assumes that the carrying amount approximates fair value due to their short maturities. Investments for which it is not practicable to estimate fair value primarily consist of investments in a number of unaffiliated and unlisted smaller sized companies and the estimate of their fair values cannot be made without incurring excessive costs. Refundable insurance policies are carried at cash surrender value. The carrying amounts for long-term borrowings with variable rates approximate their fair values. The carrying amounts and fair value of financial instruments are summarized below:
			Thousands of Yen								Thousands of
											U.S. Dollars
			2013				2014				2014
			Carrying		Fair		Carrying		Fair		Carrying		Fair
			Amount		Value		Amount		Value		Amount		Value
	Other investments for which it is:
	Practicable to estimate fair value		¥	1,309,923	¥	1,309,923	¥	3,751,011	¥	3,751,011	$	36,425	$	36,425
	Not practicable			2,461,339		-		2,604,806		-		25,294		-
	Noncurrent refundable insurance policies (other assets)			64,020		64,020		63,062		63,062		612		612
	Cash and cash equivalents were classified as Level 1 instruments and short-term and long-term borrowings were classified as Level 2 instruments.
	Other investments for which it is practicable to estimate fair value are available-for-sales equity securities disclosed in Note 4.
	Other investments for which it is not practicable to estimate fair value were comprised of non-marketable equity securities of  ¥1,121,444 thousand and investments in funds of  ¥1,339,895 thousand as of March 31, 2013 and non-marketable equity securities of ¥1,379,623 thousand ($13,397 thousand) and investments in funds of ¥1,225,183 thousand ($11,897 thousand) as of March 31, 2014.

Note_19_Fair_Value_Measurement

Note 19 - Fair Value Measurements

12 Months Ended

Mar. 31, 2014

Fair Value Disclosures [Abstract]

'

Fair Value Disclosures [Text Block]

'

19

FAIR VALUE MEASUREMENTS

ASC Topic 820, “Fair Value Measurement” defines fair value as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants at the measurement date. ASC Topic 820 establishes a three-level fair value hierarchy that prioritizes the inputs used to measure fair value as follows:

Level 1―Inputs are quoted prices in active markets for identical assets or liabilities.

Level 2―Inputs are quoted prices for similar assets or liabilities in active markets, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable, and inputs that are derived principally from or corroborated by observable market data by correlation or other means.

Level 3―Inputs are derived from valuation techniques in which one or more significant inputs or value drivers are unobservable, which reflect the reporting entity’s own assumptions about the assumptions that market participants would use in establishing a price.

There were no transfers between Level 1 and Level 2 for the years ended March 31, 2013 and 2014.

Assets Measured at Fair Value on a Recurring Basis

The following table presents the Company’s assets and liabilities that are measured at fair value on a recurring basis at March 31, 2013 and 2014, respectively, consistent with the fair value hierarchy provisions of  ASC Topic 820.

Thousands of Yen

Total

Level 1

Level 2

Level 3

2013

31-Mar-13

Assets―

Available-for-sale securities―equity securities

¥

1,309,923

-

-

¥

1,309,923

Thousands of Yen

Total

31-Mar-14

Level 1

Level 2

Level 3

2014

Assets―

Available-for-sale securities―equity  securities

¥

3,751,011

-

-

¥

3,751,011

Thousands of U.S. Dollars

Total

31-Mar-14

Level 1

Level 2

Level 3

2014

Assets―

Available-for-sale securities―equity  securities

$

36,425

-

-

$

36,425

Available-for-sale securities are comprised of marketable securities, which are listed on Japan and Hong Kong securities markets and are valued using an unadjusted quoted market price in active markets with sufficient volume and frequency of transactions.

Assets Measured at Fair Value on a Nonrecurring Basis

Thousands of Yen

31-Mar-13

Level 1

Level 2

Level 3

Impairment Loss

Assets:

Trademark

-

-

¥

107,000

¥

48,000

-

-

¥

107,000

¥

48,000

The trademark right related to hi-ho with a carrying amount of ¥155,000 thousand was written down to fair value of ¥107,000 thousand, resulting in an impairment charge of ¥48,000 thousand, which was included in the Company’s statement of income for the year ended March 31, 2013. The impaired trademark was classified within Level 3 as the Company used unobservable inputs such as expected future income to value the trademark.

With regards to Level 3 valuations, our valuation team (accounting and financing managers) decides the methodologies and performs the valuation of each instrument. We use third-party valuation firms to conduct the valuation of certain instruments, if necessary. Detailed reviews of the methodologies in valuations and the reasonableness of the valuations (including those performed by third parties) are performed by the chief financial officer.

The following table presents information relating to the significant unobservable inputs of the Company’s Level 3 non-recurring measurements.

Thousands

of Yen

31-Mar-13

Fair

Valuation

Unobservable

Range

value

technique

inputs

Trademark

¥107,000

Relief from

Discount Rate

7.50%

royalty method

Royalty rate

0.30%

Note_20_Business_Segments

Note 20 - Business Segments	12 Months Ended
	Mar. 31, 2014
Segment Reporting [Abstract]	'
Segment Reporting Disclosure [Text Block]	'
	20	BUSINESS SEGMENTS
	The operating segments reported below are those for which segment-specific financial information is available. Accounting policies used to determine segment profit/loss and segment assets are consistent with those used to prepare the consolidated financial statements in accordance with U.S. GAAP. The Company’s management uses this financial information to make decisions on the allocation of resources and to evaluate business performance.
	Network service and systems integration business segment comprises revenues from network services, systems integration and equipment sales.
	ATM operation business segment comprises revenues from the ATM operation business.
	Revenues:
			Thousands of Yen							Thousands of
										U.S. Dollars
			2012			2013		2014		2014
	Network service and systems integration business:
	Customers		¥	95,990,449		¥	103,928,400	¥	111,445,519	$	1,082,205
	Intersegment			506,030			558,753		455,975		4,428
	Total			96,496,479			104,487,153		111,901,494		1,086,633
	ATM operation business:
	Customers			1,324,156			2,320,086		2,826,832		27,450
	Intersegment		-			-		-		-
	Total			1,324,156			2,320,086		2,826,832		27,450
	Elimination			506,030			558,753		455,975		4,428
	Consolidated total		¥	97,314,605		¥	106,248,486	¥	114,272,351	$	1,109,655
	Segment Profit or Loss:
			Thousands of Yen							Thousands of
										U.S. Dollars
			2012			2013		2014		2014
	Operating income (loss):
	Network service and systems integration business		¥	6,631,476		¥	7,629,435	¥	5,274,753	$	51,221
	ATM operation business			(194,264	)		239,035		578,794		5,620
	Elimination			83,729			115,828		130,235		1,264
	Consolidated total		¥	6,353,483		¥	7,752,642	¥	5,723,312	$	55,577
	Segment Assets:
			Thousands of Yen					Thousands of
								U.S. Dollars
			2013			2014		2014
	Segment assets:
	Network service and systems integration business		¥	79,958,814		¥	100,860,325	$	979,417
	ATM operation business			2,152,452			3,006,250		29,192
	Elimination
	Consolidated total		¥	82,111,266		¥	103,866,575	$	1,008,609
	Other significant items:
			Thousands of Yen							Thousands of
										U.S. Dollars
			2012			2013		2014		2014
	Depreciation and amortization:
	Network service and systems integration business		¥	7,006,576		¥	7,178,397	¥	8,405,080	$	81,619
	ATM operation business			137,055			329,411		417,901		4,058
	Consolidated total		¥	7,143,631		¥	7,507,808	¥	8,822,981	$	85,677
	For information regarding the goodwill and the other impairment losses on intangible assets, see Note 8, “Goodwill and Other intangible assets.”
	Transfers between reportable businesses are made at market-based prices. Operating income (loss) is operating revenue less costs and operating expenses.
	Substantially all revenues are from customers operating in Japan. Geographic information is not presented due to immateriality of revenue attributable to international operations.
	Revenue from IBM Japan, Ltd., related to network service and system integration business segment represents ¥14,396,722 thousand, ¥13,456,203 thousand and ¥13,125,454 thousand ($127,456 thousand) for the years ended March 31, 2012, 2013 and 2014, respectively, of the Company’s consolidated revenue.

Note_21_Advertising_Expenses

Note 21 - Advertising Expenses	12 Months Ended
	Mar. 31, 2014
Other Income and Expenses [Abstract]	'
Other Income and Other Expense Disclosure [Text Block]	'
	21	ADVERTISING EXPENSES
	Advertising expenses incurred during the years ended March 31, 2012, 2013 and 2014 related primarily to advertisements in magazines, journals and newspapers and amounted to ¥563,051 thousand, ¥671,260 thousand and ¥656,890  thousand ($6,379  thousand), respectively.

Note_22_Related_Party_Transact

Note 22 - Related Party Transactions	12 Months Ended
	Mar. 31, 2014
Related Party Transactions [Abstract]	'
Related Party Transactions Disclosure [Text Block]	'
	22	RELATED PARTY TRANSACTIONS
	NTT and its subsidiaries own 26.0% of IIJ's outstanding common shares and 26.4% of IIJ's voting shares as of March 31, 2014.
	The Company entered into a number of different types of transactions with NTT and its subsidiaries including purchases of wireline telecommunication services for the Company’s offices. For the Company’s connectivity and outsourcing services, the Company purchases international and domestic backbone services, local access lines and rental rack space in data centers from NTT and its subsidiaries.  The Company sells to NTT and its subsidiaries its services including OEM services, system integration services and monitoring services for their data centers.
	The amounts of balances as of March 31, 2013 and 2014 and transactions of the Company with NTT and its subsidiaries for the each of the three years in the period ended March 31, 2014, are summarized as follows:
			Thousands of Yen						Thousands of
									U.S. Dollars
			2012		2013		2014		2014
	Accounts receivable			-	¥	171,909	¥	446,857	$	4,339
	Accounts payable			-		1,578,969		1,822,997		17,702
	Revenues		¥	895,189		880,079		2,370,954		23,023
	Costs			14,225,717		14,966,177		15,579,173		151,283
	As for balances and transactions with equity method investees, refer to Note 6, “Investments in Equity Method Investees.”

Note_23_Subsequent_Events

Note 23 - Subsequent Events	12 Months Ended
	Mar. 31, 2014
Subsequent Events [Abstract]	'
Subsequent Events [Text Block]	'
	23	SUBSEQUENT EVENTS
	On June 25, 2014, IIJ’s shareholders approved the payment of a cash dividend to shareholders of record at March 31, 2014 of ¥11 ($0.11) per share or in the aggregate amount of ¥505,330 thousand ($4,907 thousand).

Accounting_Policies_by_Policy_

Accounting Policies, by Policy (Policies)	12 Months Ended
	Mar. 31, 2014
Accounting Policies [Abstract]	'
Basis of Accounting, Policy [Policy Text Block]	'
	Basis of Presentation—IIJ maintains its records and prepares its financial statements in accordance with generally accepted accounting principles in Japan. Certain adjustments and reclassifications have been incorporated in the accompanying consolidated financial statements to conform to generally accepted accounting principles in the United States of America ("U.S. GAAP"). These adjustments were not recorded in the statutory accounts.
Reclassification, Policy [Policy Text Block]	'
	Reclassification－Certain reclassifications have been made to prior periods to conform to the current year presentations: (1) “Guarantee deposits―current,” which had been previously included in "Other current assets," was separately disclosed as the amount was deemed material. (2) “Increase in inventories, prepaid expenses and other current and noncurrent assets” was divided into “Increase in inventories”, “Increase in prepaid expenses” and “Increase in other current and noncurrent assets” as the amounts were deemed material.
Translation Into U.S. Dollars [Policy Text Block]	'
	Translation into U.S. Dollars—IIJ maintains its accounts in Japanese yen, the currency of the country in which it is incorporated and principally operates. The U.S. dollar amounts included herein represent a translation using the noon buying rate in New York City for cable transfers in yen as certified for customs purposes by the Federal Reserve Bank of New York at March 31, 2014 of ¥102.98 =160;$1, solely for the convenience of the reader. The translation should not be construed as a representation that the yen amounts have been, could have been, or could in the future be converted into U.S. dollars.
Consolidation, Policy [Policy Text Block]	'
	Consolidation—The consolidated financial statements include the accounts of IIJ and all of its subsidiaries, Net Care, Inc. ("Net Care"), IIJ America, Inc. ("IIJ-America"), Netchart Japan Inc. ("NCJ"), hi-ho Inc. ("hi-ho"), Trust Networks Inc. ("Trust Networks"), IIJ Innovation Institute Inc. ("IIJ-II"), IIJ Global Solutions Inc. ("IIJ-Global") and its subsidiaries, IIJ Exlayer Inc. ("IIJ-Exlayer") and its subsidiaries and IIJ Europe Limited ("IIJ-Europe"). IIJ-Global was acquired by IIJ on September 1, 2010. IIJ-Exlayer was acquired by IIJ on April 2, 2012. IIJ-Europe was originally a wholly-owned subsidiary of IIJ-Exlayer. IIJ-Exlayer was merged with IIJ on January 1, 2014. GDX Japan Inc. (“GDX”) was established on April 16, 2007 and liquidated on March 16, 2012. All of the subsidiaries, except for IIJ-Exlayer, IIJ-America, IIJ-Europe and other foreign subsidiaries, have fiscal years ending March 31. IIJ-Exlayer, IIJ-America, IIJ-Europe and other foreign subsidiaries’ fiscal year-end is December 31 and such date was used for purposes of preparing the consolidated financial statements as it is not practicable for the foreign subsidiaries to report their financial results as of March 31. There were no significant events that occurred during the intervening period that would require adjustment to or disclosure in the accompanying consolidated financial statements. Intercompany transactions and balances have been eliminated in consolidation.
	Investments in companies over which IIJ has significant influence but not control are accounted for by the equity method. For other than a temporary decline in the value of investments in equity method investees below the carrying amount, the investment is reduced to fair value and an impairment loss is recognized.
	Equity-method goodwill which is the portion of the difference between the cost of an investment and the amount of underlying equity in net assets of an investee is not amortized, but equity-method investments shall continue to be reviewed for impairment in accordance with Accounting Standards Codification (“ASC”)  323 “Investments-Equity Method and Joint Ventures.”
	A subsidiary or equity method investee may issue its shares to third parties at amounts per share in excess of or less than the Company’s average per share carrying value. Changes in a parent’s ownership interest while the parent retains its controlling financial interest in its subsidiary are accounted for as equity transactions.
Use of Estimates, Policy [Policy Text Block]	'
	Use of Estimates—The preparation of financial statements in conformity with generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting period. Significant estimates and assumptions used are primarily in the areas of evaluation of investments, valuation allowances for deferred tax assets, allowance for doubtful accounts, determination of pension benefit costs and obligations, estimated useful lives of fixed assets and intangible assets with finite useful lives and impairment of long-lived assets, goodwill and intangible assets deemed to have indefinite useful lives. Actual results could differ from those estimates.
Revenue Recognition, Policy [Policy Text Block]	'
	Revenue Recognition—Network service revenues are billed and recognized monthly on a straight-line basis. Initial set up fees received in connection with network services are deferred and recognized over the estimated average period of the subscription for each service.
	System integration and service arrangements involve the following deliverables:
		●	System construction services ― include all or some of the following elements depending on arrangements to meet each of our customer's requirements: consulting, project planning, system design, and development of network systems. These services also include the installation of software as well as configuration and installationof hardware.
		●	Software ― we resell third-party software such as Oracle and Windows to our customers, which are installed by us during the system development process.
		●	Hardware ― we also resell third-party hardware, primarily servers, switches and routers, which we install during the system development process. The hardware is generic hardware that is often sold by third party manufacturers and resellers.
		●	Monitoring and operating service ― we monitor our customer's network activity and internet connectivity to detect and report problems. We also provide constant data backup services.
		●	Hardware and software maintenance service ― we repair or replace any malfunctioning parts of hardware. We examine software faults and provide suitable solutions to customers.
	The system construction services are generally delivered over a three-month period. All hardware and software are delivered and installed during this period. Customers are required to pay a specified fixed fee that is not payable until after the system construction has been completed and accepted by our customers.
	Monitoring, operating, and hardware and software maintenance services generally commence once our customers have accepted the systems, and contract periods are generally from one to five years. Our contracts include a stated annual fee for these services.
	For multiple-element arrangements that include system construction service, hardware, software essential to the hardware product’s functionality and undelivered non-software services (e.g., monitoring and operating services), the Company allocates revenue to all deliverables based on their relative selling prices. The Company uses a hierarchy to determine the selling price to be used for allocating revenue to deliverables: (i) vendor-specific objective evidence of fair value (“VSOE”), (ii) third-party evidence of selling price (“TPE”) and (iii) best estimate of the selling price (“ESP”). The allocation of revenue is based mainly on the Company’s ESPs except for certain undelivered non-software services for which VSOE has been established. The Company’s process for determining its ESP for deliverables includes various factors that may vary depending on the circumstances and specific characteristics related to each deliverable. In developing the ESP, the Company considers customer demand, the existence and effect of competitors, general profit margin realized in the marketplace, volume of the transactions, the Company’s internal costs of providing the deliverables, the profit objectives including targeted and historical margins realized on similar sales to similar customers and the historical pricing practices.
	The method used to account for each unit and the period over which each unit of accounting is recognized are as follows:
		●	Revenue allocated to system construction services is accounted for using contract accounting. System construction service revenues, which are generally completed within three months, are recognized based on the completed-contract method in compliance with ASC 605-35-25-92 because the Company is unable to bill customers and the title to the constructed network system is not transferred to the customers unless they are satisfied with and accept the completed systems.
		●	Revenue related to the hardware and software essential to the hardware product’s functionality is not recognized until customer acceptance is received because title to the hardware and software do not transfer to our customers until formal acceptance is received.
		●	Revenue related to undelivered non-software services (monitoring, operating and hardware maintenance services) is recognized on a straight-line basis over the contract period.
	The Company also enters into multiple-element arrangements for system integration services that include software not essential to the hardware product’s functionality and software-related services and account for them in accordance with ASC 985-605, “Software-Revenue Recognition”. The Company has been able to establish VSOE of fair value of the software-related services based on separate renewal contracts of the services that are consistently priced within a narrow range. The Company allocates revenue to such services based on VSOE and recognizes the revenues on a straight-line basis over the contract period. The Company allocates the residual amount to the software and system construction services.
	Equipment sales revenues are recognized when equipment is delivered and accepted by the customer.
	The Company evaluates whether it is appropriate to record the gross amount of revenues and related costs or the net amount earned in reporting system construction services and equipment sales, depending on whether the Company functions as principal or agent.
	ATM operation business revenues consist primarily of commissions for each withdrawing transaction with the use of ATMs. ATM commission collected from each withdrawal is aggregated every month and recognized as ATM operation revenues.
	Revenue is recognized net of consumption tax collected from customers and subsequently remitted to governmental authorities.
Cash and Cash Equivalents, Policy [Policy Text Block]	'
	Cash and Cash Equivalents—Cash and cash equivalents includes time deposit with original maturities of three months or less.
Loans and Leases Receivable, Allowance for Loan Losses Policy [Policy Text Block]	'
	Allowance for Doubtful Accounts—An allowance for doubtful accounts is established in amounts considered to be appropriate based primarily upon the Company's past credit loss experience and an evaluation of potential losses in the receivables outstanding.
Investment, Policy [Policy Text Block]	'
	Other Investments—The Company classifies its marketable equity securities as available-for-sale securities, which are accounted for at fair value with unrealized gains and losses excluded from earnings and reported in accumulated other comprehensive income (loss). The cost of securities sold is determined based on average cost.
	The Company reviews the fair value of available-for-sale securities on a regular basis to determine if the fair value of any individual security has declined below its cost and if such decline is other-than-temporary.  If the decline in value is judged to be other-than-temporary, the cost basis of the investment is written down to fair value. Other-than-temporary declines in value are determined taking into consideration the extent of decline in fair value, the length of time that the decline in fair value below cost has existed and events that might accelerate the recognition of impairment. The resulting realized loss is included in the consolidated statements of income in the period in which the decline is deemed to be other-than-temporary.
	Non-marketable equity securities are carried at cost as fair value is not readily determinable. When the Company evaluates whether non-marketable equity securities are impaired or not, the Company evaluates first whether an event or change in circumstances has occurred in the period that may have significant adverse effect on the fair value of the securities (an impairment indicator). The Company uses such impairment indicators as follows:
		●	A significant deterioration in the earnings performance or business prospects of the investee.
		●	A significant adverse change in the regulatory, economic, or technological environment of the investee.
		●	A significant adverse change in the general market condition of either the geographic area or the industry in which the investee operates.
		●	A recent example of the new issuance of a security, in which the issue price is less than our cost.
	The Company estimates the fair value of the non-marketable equity securities when an impairment indicator is present. The fair value is determined as a result of considering various unobservable inputs which are available to the Company, including expectation of future income of the investees, net asset value of the investees, and material unrealized losses to be considered in assets and liabilities held by the investees. The Company recognizes impairment of non-marketable equity securities when the fair value is below the carrying amount and the decline in fair value is considered to be other-than-temporary.
Inventory, Policy [Policy Text Block]	'
	Inventories—Inventories consist mainly of network equipment purchased for resale and work-in-process for construction of network systems. Network equipment purchased for resale is stated at the lower of cost, which is determined by the average-cost method, or market.  Work-in-process for development of network systems is stated at the lower of actual production costs, including overhead cost, or market.  Inventories are reviewed periodically and items considered to be slow-moving or obsolete are written down to their estimated net realizable value.
Lease, Policy [Policy Text Block]	'
	Leases—Capital leases are capitalized at the inception of the lease at the present value of the minimum lease payments. All other leases are accounted for as operating leases. Lease payments for capital leases are apportioned to interest expense and a reduction of the lease liability so as to achieve a constant rate of interest on the remaining balance of the liability. Operating lease payments are recognized as an expense on a straight-line basis over the lease term.
Revenue Recognition Leases, Capital [Policy Text Block]	'
	Sales-Type Leases—The Company has some sales-type lease agreements with customers. The Company recognizes revenues on sales-type leases when the assets under lease are delivered to and accepted by the customers. The revenue recognized is calculated at the net present value of the future receipt amounts. Interest income in sales-type leases is recognized in other income using the interest method.
Property, Plant and Equipment, Policy [Policy Text Block]	'
	Property and Equipment—Property and equipment are recorded at cost. Depreciation and amortization of property and equipment, including capitalized software and capital leases, are computed principally using the straight-line method based on either the estimated useful lives of assets or the lease period, whichever is shorter.
	The useful lives for depreciation and amortization by major asset classes are as follows:
			Range of
			Useful Lives
	Data communications, office and other equipment (years)		3	to	20
	Buildings (years)			20
	Leasehold improvements (years)		8	to	20
	Capitalized software (years)			5
	Capital leases (years)		4	to	6
Impairment or Disposal of Long-Lived Assets, Policy [Policy Text Block]	'
	Impairment of Long-Lived Assets—Long-lived assets consist principally of property and equipment, including those items leased under capital leases and amortized intangible assets. The Company evaluates the impairment of long-lived assets whenever events or changes in circumstances indicate that the carrying amount of an asset or asset group may not be recoverable. Long-lived assets to be held and used are reviewed for impairment by comparing the carrying amount of the asset or asset group with their estimated undiscounted future cash flows. If the cash flows are determined to be less than the carrying amount of the asset or asset group, an impairment loss has occurred and the loss would be recognized during the period for the difference between the carrying amount of the asset or asset group and estimated fair value.
Goodwill and Intangible Assets, Goodwill, Policy [Policy Text Block]	'
	Goodwill and Intangible Assets—Goodwill and intangible assets that are deemed to have indefinite useful lives are not amortized, but are subject to impairment testing.  Impairment testing is performed annually or more frequently if events or changes in circumstances indicate that the asset might be impaired. The Company performs annual impairment tests on March 31. If the carrying amount of a reporting unit exceeds its fair value, the Company then performs the second step of the goodwill impairment test to measure the amount of impairment loss, if any. Intangible assets with finite useful lives, consisting of customer relationships, are amortized using a non-straight-line basis based on the pattern of expected future economic benefit over the estimated useful lives, which range from 6 to 19 years.
Asset Retirement Obligations, Policy [Policy Text Block]	'
	Asset Retirement Obligations—The Company records the fair value of a liability for an asset retirement obligation in the period in which it is incurred. When the liability is initially recorded, the Company capitalizes the related cost by increasing the carrying amount of long-lived asset. Over time, the liability is accreted to its present value each period, and the capitalized cost is depreciated for the period the Company has estimated.
Pension and Other Postretirement Plans, Policy [Policy Text Block]	'
	Pension and Severance Indemnities Plans—The Company has defined benefit pension plans and severance indemnities plans. The cost of the pension plans and severance indemnities plans are accrued based on amounts determined using actuarial methods. In addition, the Company has defined contribution pension plans. The costs of defined contribution pension plans are charged to expenses when incurred.
Income Tax, Policy [Policy Text Block]	'
	Income Taxes—Income tax expense is based on reported earnings before income taxes. Deferred income taxes reflect the impact of temporary differences between assets and liabilities recognized for financial reporting purposes and such amounts recognized for tax purposes and tax loss carryforwards. These deferred taxes are measured using the currently enacted tax rates in effect for the year in which the temporary differences or tax loss carryforwards are expected to reverse. Valuation allowances are provided against deferred tax assets when it is more likely than not that a tax benefit will not be realized.
	The Company recognizes the financial statement effect of uncertain tax positions when they are more-likely- than not, based on the technical merits, that the tax positions will be sustained upon examination by the tax authorities. Benefits from tax positions that meet the more-likely-than-not recognition threshold are measured at the largest amount of benefit that is greater than 50% likely of being realized upon settlement. Interest and penalties accrued related to unrecognized tax benefits are included in income tax expense in the consolidated statements of income.
Foreign Currency Transactions and Translations Policy [Policy Text Block]	'
	Foreign Currency Translation—The assets and liabilities of a foreign subsidiary and an equity method investee are translated into Japanese yen at the respective year-end exchange rates. All income and expense accounts are translated at average rates of exchange. The resulting translation adjustments are included in accumulated other comprehensive income.
	Foreign currency assets and liabilities, which consist substantially of cash denominated in U.S. dollars, are stated at the amount as computed by using year-end exchange rates and the resulting transaction gain or loss is recognized in earnings.
Stockholders' Equity, Policy [Policy Text Block]	'
	Stock Splits―On September 6, 2012, IIJ’s board of directors approved a two hundred-for-one split of IIJ’s common stock. Shareholders of record on September 30, 2012 received an additional common share. The stock split was effective on October 1, 2012. In order to reflect this split, information pertaining to shares and earnings per share has been restated in the accompanying financial statements and related notes.
Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block]	'
	Stock-Based Compensation—The Company measures and records the compensation cost from stock compensation-type stock option based on fair value. The fair value of the stock option is measured on the date of grant using the Black-Scholes option-pricing model, and amortized over the requisite service period. The compensation cost is mainly included in “General and administrative” expenses.
Research, Development, and Computer Software, Policy [Policy Text Block]	'
	Research and Development and Capitalized Software Development Costs—Research and development costs are expensed as incurred, which include research and development costs incurred for computer software to be leased. Software development costs incurred subsequent to establishing technological feasibility through the general release of the software products are capitalized. Technological feasibility is demonstrated by the completion of a detailed program design. Capitalized costs are amortized based on either the ratio of the current revenues to the total estimated revenues over the estimated useful lives (generally five years) or the equally allocated amount over the residual useful lives, whichever is larger.
Advertising Costs, Policy [Policy Text Block]	'
	Advertising—Advertising costs are expensed as incurred and are recorded in “Sales and marketing.”
Earnings Per Share, Policy [Policy Text Block]	'
	Basic and Diluted Net Income attributable to Internet Initiative Japan Inc. per Common Share—Basic net income attributable to Internet Initiative Japan Inc. per common share is computed by dividing net income attributable to Internet Initiative Japan Inc. by the weighted-average number of shares of common stock outstanding during the year. Diluted net income attributable to Internet Initiative Japan Inc. per common share reflects the potential dilutive effect of stock options.
Comprehensive Income, Policy [Policy Text Block]	'
	Other Comprehensive Income (Loss)—Other comprehensive income (loss) consists of translation adjustments resulting from the translation of financial statements of a foreign subsidiary, unrealized gains or losses on available-for-sale securities and defined benefit pension plans adjustment.
Segment Reporting, Policy [Policy Text Block]	'
	Segment Reporting—ASC Topic 280, “Segment Reporting” establishes standards for reporting information about operating segments. Operating segments are defined as components of an enterprise that engage in business activities from which it may earn revenues and incur expense and for which separate financial information is available that is evaluated regularly by the chief operation decision maker in deciding how to allocate resources and in assessing performance.
	The Company provides a comprehensive range of network solutions to meet its customers’ needs by cross-selling a variety of services, including Internet connectivity services, WAN services, outsourcing services, systems integration and sales of network-related equipment, and ATM operation services. The Company’s chief operating decision maker, who is the Company’s Chief Operating Officer ("COO"), regularly reviews the revenue and cost of sales on the two operating segments, which are Network service and systems integration business segment, and ATM operation business segment. The COO also makes decisions regarding how to allocate resources and assess performance based on the segments.
New Accounting Pronouncements, Policy [Policy Text Block]	'
	New Accounting Guidance
	In December 2011, the FASB issued Accounting Standards Update (“ASU”) 2011-11, "Balance Sheet: Disclosures about Offsetting Assets and Liabilities," which requires new disclosures about financial instruments and derivative instruments that are either offset by or subject to an enforceable master netting arrangement or similar agreement. In January 2013, the FASB issued ASU 2013-01, "Balance Sheet: Clarifying the Scope of Disclosures about Offsetting Asset and Liabilities," which clarifies the scope of the offsetting disclosures of ASU 2011-11. Both ASUs are effective for fiscal years beginning on or after January 1, 2013 and interim periods within those years and the Company adopted this ASU in the first quarter beginning April 1, 2013. The adoption of this ASU did not have a material impact on the Company’s financial position or results of operations.
	In July 2012, the FASB issued ASU 2012-02, "Intangibles－Goodwill and Other: Testing Indefinite-Lived Intangible Assets for Impairment," which provides new guidance on the annual indefinite-lived intangible assets impairment testing. The objective of the amendments in this Update is to reduce the cost and complexity of performing an impairment test for indefinite-lived intangible assets by simplifying how an entity tests those assets for impairment and to improve consistency in impairment testing guidance among long-lived asset categories. The amendments permit an entity first to assess qualitative factors to determine whether it is more likely than not that an indefinite-lived intangible asset is impaired as a basis for determining whether it is necessary to perform the quantitative impairment test in accordance with Subtopic 350-30, “Intangibles—Goodwill and Other—General Intangibles Other than Goodwill”. This ASU is effective for annual and interim indefinite-lived intangible assets impairment tests performed for fiscal years beginning after September 15, 2012 and the Company adopted this ASU in the first quarter beginning April 1, 2013. The adoption of this ASU did not have a material impact on the Company’s financial position or results of operations.
	In February 2013, the FASB issued ASU 2013-02, “Comprehensive Income: Reporting of Amounts Reclassified out of Accumulated Other Comprehensive Income,” which requires entities to provide information about the amounts reclassified out of accumulated other comprehensive income by component, and to present, either on the face of the statement where net income is presented or in the notes, significant amounts reclassified out of accumulated other comprehensive income by the respective line items of net income. This ASU is effective for fiscal years, and interim periods within those years, beginning after December 15, 2012 and the Company adopted this ASU in the first quarter beginning April 1, 2013. The adoption of this ASU did not have a material impact on the Company’s financial position or results of operations. See Note 15 for the disclosures related to this adoption.
New Accounting Pronouncements Not Yet Adopted, Policy [Policy Text Block]	'Accounting Guidance Issued But Not Adopted as of March 31, 2014In July 2013, the FASB issued ASU 2013-11, "Income Taxes: Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists," which defines the presentation requirements of an unrecognized tax benefit, or a portion of an unrecognized tax benefit, in the financial statements. This ASU is effective for fiscal years, and interim periods within those years, beginning after December 15, 2013. Early adoption is permitted and retrospective application is permitted, but not required. The adoption of this ASU will not have a material impact on the Company's financial position or results of operations.In May 2014, the FASB issued ASU 2014-09, "Revenue from Contracts with Customers," to clarify the principles for recognizing revenue and to develop a common revenue standard for U.S.GAAP and International Financial Reporting Standards. This guidance also requires an entity to improve disclosures to enable users of financial statements to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. This ASU is effective for fiscal years, and interim periods within those years, beginning after December 15, 2016. The Company is currently evaluating the impact of adopting this guidance .

Note_1_Description_of_Business1

Note 1 - Description of Business and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Mar. 31, 2014
Accounting Policies [Abstract]	'
Property, Plant and Equipment, Useful Lives [Table Text Block]	'
		Range of
		Useful Lives
	Data communications, office and other equipment (years)	3	to	20
	Buildings (years)		20
	Leasehold improvements (years)	8	to	20
	Capitalized software (years)		5
	Capital leases (years)	4	to	6

Note_3_Inventory_Tables

Note 3 - Inventory (Tables)	12 Months Ended
	Mar. 31, 2014
Inventory Disclosure [Abstract]	'
Schedule of Inventory, Current [Table Text Block]	'
		Thousands of Yen				Thousands of
						U.S. Dollars
		2013		2014		2014
	Network equipment purchased for resale	¥	350,976	¥	503,334	$	4,888
	Work in process		950,708		1,166,924		11,331
	Total inventories	¥	1,301,684	¥	1,670,258	$	16,219

Note_4_Other_Investments_Table

Note 4 - Other Investments (Tables)	12 Months Ended
	Mar. 31, 2014
Note 4 - Other Investments (Tables) [Line Items]	'
Available-for-sale Securities [Table Text Block]	'
		Thousands of U.S. Dollars
	31-Mar-14	Cost		Unrealized		Unrealized		Fair
				Gains		Losses		Value
	Available-for-sale—Equity securities	$	13,515	$	22,961	$	51	$	36,425
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Table Text Block]	'
		Thousands of U.S. Dollars
		Less than				12 Months or More				Total
		12 Months
	31-Mar-14	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
		Value		Losses		Value		Losses		Value		Losses
	Available-for-sale—Equity securities	$	549	$	51		-		-	$	549	$	51
Japanese Yen [Member]	'
Note 4 - Other Investments (Tables) [Line Items]	'
Available-for-sale Securities [Table Text Block]	'
		Thousands of Yen
	31-Mar-13	Cost		Unrealized		Unrealized		Fair
				Gains		Losses		Value
	Available-for-sale—Equity securities	¥	500,616	¥	813,445	¥	4,138	¥	1,309,923
	31-Mar-14
	Available-for-sale—Equity securities	¥	1,391,820	¥	2,364,442	¥	5,251	¥	3,751,011
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value [Table Text Block]	'
		Thousands of Yen
		Less than				12 Months or More				Total
		12 Months
	31-Mar-13	Fair		Unrealized		Fair		Unrealized		Fair		Unrealized
		Value		Losses		Value		Losses		Value		Losses
	Available-for-sale—Equity securities	¥	27,902	¥	4,138		-		-	¥	27,902	¥	4,138
	31-Mar-14
	Available-for-sale—Equity securities	¥	56,524	¥	5,251		-		-	¥	56,524	¥	5,251

Note_5_Allowance_for_Doubtful_1

Note 5 - Allowance for Doubtful Accounts and Loans (Tables)	12 Months Ended
	Mar. 31, 2014
Japan, Yen	'
Note 5 - Allowance for Doubtful Accounts and Loans (Tables) [Line Items]	'
Allowance for Credit Losses on Financing Receivables [Table Text Block]	'
		Thousands of Yen
		Balance at		Credits			Provision for			Other		Balance at
		Beginning of		Charged Off			(Reversal of)					End of Year
		Year					Doubtful
							Accounts
	Year ended March 31, 2012	¥	142,871	¥	(19,878	)	¥	82,046			-	¥	205,039
	Year ended March 31, 2013	¥	205,039	¥	(17,934	)	¥	(10,712	)		-	¥	176,393
	Year ended March 31, 2014	¥	176,393	¥	(12,067	)	¥	(46,935	)		-	¥	117,391
United States of America, Dollars	'
Note 5 - Allowance for Doubtful Accounts and Loans (Tables) [Line Items]	'
Allowance for Credit Losses on Financing Receivables [Table Text Block]	'
		Thousands of U.S. Dollars
		Balance at		Credits			Reversal of			Other		Balance at
		Beginning of		Charged Off			Doubtful					End of Year
		Year					Accounts
	Year ended March 31, 2014	$	1,713	$	(117	)	$	(456	)		-	$	1,140

Note_6_Investments_in_Equity_M1

Note 6 - Investments in Equity Method Investees (Tables)	12 Months Ended
	Mar. 31, 2014
Note 6 - Investments in Equity Method Investees (Tables) [Line Items]	'
Schedule of Related Party Transactions [Table Text Block]	'
		Thousands of Yen								Thousands of
										U.S. Dollars
		2012			2013		2014			2014
	Accounts receivable		-		¥	171,909	¥	446,857		$	4,339
	Accounts payable		-			1,578,969		1,822,997			17,702
	Revenues	¥	895,189			880,079		2,370,954			23,023
	Costs		14,225,717			14,966,177		15,579,173			151,283
Equity Method Investments [Table Text Block]	'
		Thousands of Yen										Thousands of
												U.S. Dollars
		2013					2014					2014
	Multifeed		33	%	¥	1,141,909		33	%	¥	1,244,512	$	12,085
	i-revo		30			371,888		30			529,142		5,138
	Trinity		33.75			93,154		33.75			88,804		862
	Stratosphere		50			74,772		50			32,451		315
	Appiaries		-			-		49			190,780		1,853
	Total				¥	1,681,723				¥	2,085,689	$	20,253
Equity Method Investee [Member]	'
Note 6 - Investments in Equity Method Investees (Tables) [Line Items]	'
Schedule of Related Party Transactions [Table Text Block]	'
		Thousands of Yen								Thousands of
										U.S. Dollars
		2012			2013		2014			2014
	Accounts receivable		-		¥	52,422	¥	43,170		$	419
	Accounts payable		-			39,734		40,613			394
	Revenues	¥	624,718			598,765		538,288			5,227
	Costs and expenses		403,400			456,892		451,342			4,383

Note_7_Property_and_Equipment_

Note 7 - Property and Equipment (Tables)	12 Months Ended
	Mar. 31, 2014
Note 7 - Property and Equipment (Tables) [Line Items]	'
Property, Plant and Equipment [Table Text Block]	'
		Thousands of Yen						Thousands of
								U.S. Dollars
		2013			2014			2014
	Data communications equipment	¥	6,746,069		¥	8,656,572		$	84,061
	Office and other equipment		2,130,160			3,375,846			32,782
	Land		-			532,997			5,176
	Buildings		668,631			1,615,081			15,683
	Leasehold improvements		2,666,584			3,641,072			35,357
	Capitalized software		18,465,716			21,006,728			203,988
	Assets under capital leases, primarily data communications equipment		21,864,989			22,868,800			222,070
	Total		52,542,149			61,697,096			599,117
	Less accumulated depreciation and amortization		(29,516,394	)		(34,725,611	)		(337,207	)
	Property and equipment—net	¥	23,025,755		¥	26,971,485		$	261,910
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]	'
	Year Ending March 31	Thousands of Yen			Thousands of
					U.S. Dollars
	2015	¥	397,031			3,855
	2016		388,014			3,768
	2017		380,496			3,695
	2018		365,460			3,549
	2019		355,410			3,451
Software To Be Leased [Member]	'
Note 7 - Property and Equipment (Tables) [Line Items]	'
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]	'
	Year Ending March 31	Thousands of Yen			Thousands of
					U.S. Dollars
	2015	¥	619,166		$	6,013
	2016		677,298			6,577
	2017		526,416			5,112
	2018		523,848			5,087
	2019		185,607			1,802

Note_8_Goodwill_and_Other_Inta1

Note 8 - Goodwill and Other Intangible Assets (Tables)	12 Months Ended
	Mar. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]	'
Schedule of Intangible Assets and Goodwill [Table Text Block]	'
		Thousands of Yen						Thousands of
								U.S. Dollars
		2013			2014			2014
	Intangible assets subject to amortization:
	Customer relationships	¥	6,424,471			6,424,471		$	62,386
	Total		6,424,471			6,424,471			62,386
	Less accumulated amortization
	Customer relationships		(1,759,440	)		(2,222,514	)		(21,582	)
	Total		(1,759,440	)		(2,222,514	)		(21,582	)
	Intangible assets subject to amortization—net		4,665,031			4,201,957			40,804
	Intangible assets not subject to amortization:
	Telephone rights		19,400			29,987			291
	Trademark		107,000			107,000			1,039
	Goodwill		5,969,951			5,969,951			57,972
	Total		6,096,351			6,106,938			59,302
	Total intangible assets	¥	10,761,382			10,308,895		$	100,106
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense [Table Text Block]	'
	Year Ending March 31	Thousands of Yen			Thousands of
					U.S. Dollars
	2015	¥	397,031			3,855
	2016		388,014			3,768
	2017		380,496			3,695
	2018		365,460			3,549
	2019		355,410			3,451
Schedule of Goodwill [Table Text Block]	'
		Thousands of Yen									Thousands of U.S. Dollars
		Network			ATM			Total			Network			ATM		Total
		Service and			Operation						Service and			Operation
		Systems			Business						Systems			Business
		Integration									Integration
		Business									Business
	Balance at March 31, 2012
	Goodwill	¥	5,673,064		¥	235,551		¥	5,908,615
	Accumulated impairment losses		(120,282	)		-			(120,282	)
			5,552,782			235,551			5,788,333
	Acquisition		181,618			-			181,618
	Impairment losses		-			-			-
	Balance at March 31, 2013
	Goodwill		5,854,682			235,551			6,090,233		$	56,853		$	2,287	$	59,140
	Accumulated impairment losses		(120,282	)		-			(120,282	)		(1,168	)		-		(1,168	)
			5,734,400			235,551			5,969,951			55,685			2,287		57,972
	Acquisition		-			-			-			-			-		-
	Impairment losses		-			-			-			-			-		-
	Balance at March 31, 2014
	Goodwill		5,854,682			235,551			6,090,233			56,853			2,287		59,140
	Accumulated impairment losses		(120,282	)		-			(120,282	)		(1,168	)		-		(1,168	)
		¥	5,734,400		¥	235,551		¥	5,969,951		$	55,685		$	2,287	$	57,972

Note_9_Leases_Tables

Note 9 - Leases (Tables)	12 Months Ended
	Mar. 31, 2014
Note 9 - Leases (Tables) [Line Items]	'
Schedule of Lease Refundable Deposits [Table Text Block]	'
		Thousands of Yen				Thousands of
						U.S. Dollars
		2013		2014		2014
	Head office*	¥	1,472,311	¥	666,480	$	6,472
	Sales and subsidiaries offices		543,181		554,610		5,386
	Others		35,957		43,445		422
	Total refundable guarantee deposits	¥	2,051,449	¥	1,264,535	$	12,280
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	'
		Thousands of Yen						Thousands of U.S. Dollars
		Connectivity		Other		Capital		Connectivity		Other		Capital
		Lines		Operating		Leases		Lines		Operating		Leases
		Operating		Leases				Operating		Leases
		Leases						Leases
	Year ending March 31:
	2015	¥	1,914	¥	2,100,021	¥	3,895,597	$	19	$	20,393	$	37,828
	2016				2,792,711		2,721,272				27,119		26,425
	2017				2,796,420		1,442,649				27,155		14,009
	2018				544,892		446,161				5,291		4,333
	2019				47,999		113,880				466		1,106
	2020 and thereafter				83,002						806
	Total minimum lease payments	¥	1,914	¥	8,365,045		8,619,559	$	19	$	81,230		83,701
	Less amounts representing interest						263,211						2,556
	Present value of net minimum capital lease payments						8,356,348						81,145
	Less current portion						3,753,026						36,444
	Noncurrent portion					¥	4,603,322					$	44,701
Sale-Type Leases [Member]	'
Note 9 - Leases (Tables) [Line Items]	'
Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]	'
		Thousands of Yen				Thousands of
						U.S. Dollars
		2013		2014		2014
	Year ending March 31:
	2015			¥	673,758	$	6,543
	2016				537,130		5,216
	2017				153,049		1,486
	2018				69,177		672
	2019				1,701		16
	Total minimum lease payments to be received*	¥	1,405,258	¥	1,434,815	$	13,933
	Estimated residual value of leased property (unguaranteed)		-		-		-
	Less unearned income		30,400		22,364		217
	Net investment in sales-type leases		1,374,858		1,412,451		13,716
	Less current portion		476,818		659,677		6,406
	Non-current net investment in sales-type leases	¥	898,040	¥	752,774	$	7,310

Note_10_Asset_Retirement_Oblig1

Note 10 - Asset Retirement Obligations (Tables)	12 Months Ended
	Mar. 31, 2014
Asset Retirement Obligation Disclosure [Abstract]	'
Schedule of Asset Retirement Obligations [Table Text Block]	'
		Thousands of Yen				Thousands of
						U.S. Dollars
		2013		2014		2014
	Balance at beginning of the year	¥	299,083	¥	334,585	$	3,249
	Liabilities incurred		26,620		122,157		1,186
	Liabilities settled		-		-		-
	Accretion expense		8,882		8,041		78
	Revision in estimated cash flows related to head office relocation		-		48,657		473
	Balance at end of the year	¥	334,585	¥	513,440	$	4,986

Note_11_Borrowings_Tables

Note 11 - Borrowings (Tables)	12 Months Ended
	Mar. 31, 2014
Debt Disclosure [Abstract]	'
Schedule of Long-term Debt Instruments [Table Text Block]	'
		Thousands of Yen						Thousands of
								U.S. Dollars
		2013			2014			2014
	Long-term installment payable at various dates through calendar 2014. Interest is payable at variable rates based on Tokyo InterBank Offered Rate (TIBOR) which were 0.250% and 0.212% as of March 31, 2013 and 2014, respectively. Weighted average interest rates were 0.962% and 0.901% at March 31, 2013 and 2014, respectively.	¥	1,990,000		¥	980,000		$	9,517
	Less current portion		(1,010,000	)	(980,000		)		( 9,517	)
	Long-term borrowings, less current portion	¥	980,000		¥	-		$	-
Schedule of Maturities of Long-term Debt [Table Text Block]	'
		Thousands of Yen			Thousands of
					U.S. Dollars
	Year ending March 31:
	2015	¥	980,000		$	9,517

Note_12_Income_Taxes_Tables

Note 12 - Income Taxes (Tables)	12 Months Ended
	Mar. 31, 2014
Income Tax Disclosure [Abstract]	'
Schedule of Income before Income Tax, Domestic and Foreign [Table Text Block]	'
		Thousands of Yen									Thousands of
											U.S. Dollars
		2012			2013			2014			2014
	Income from operations before income tax expense and equity in net income of equity method investees:
	Domestic	¥	5,970,007		¥	7,825,846		¥	6,406,153		$	62,208
	Foreign		6,213			(68,982	)		(131,262	)		(1,275	)
	Total	¥	5,976,220		¥	7,756,864		¥	6,274,891		$	60,933
	Income taxes―current:
	Domestic	¥	2,489,350		¥	3,140,964		¥	2,453,549		$	23,825
	Foreign		422			(6,254	)		41,582			404
	Total	¥	2,489,772		¥	3,134,710		¥	2,495,131		$	24,229
	Income taxes―deferred:
	Domestic	¥	35,714		¥	(528,832	)	¥	(729,822	)	$	(7,087	)
	Foreign		-			1,704			29,996			291
	Total	¥	35,714		¥	(527,128	)	¥	(699,826	)	$	(6,796	)
Schedule of Deferred Tax Assets and Liabilities [Table Text Block]	'
		Thousands of Yen												Thousands of U.S. Dollars
		2013						2014						2014
		Deferred			Deferred			Deferred			Deferred			Deferred			Deferred
		Tax			Tax			Tax			Tax			Tax			Tax
		Assets			Liabilities			Assets			Liabilities			Assets			Liabilities
	Unrealized gains on available‑for‑sale securities		-		¥	290,623			-		¥	847,033			-		$	8,225
	Capital leases	¥	73,735			-		¥	106,807			-		$	1,037			-
	Accrued expenses		713,056			-			748,875			-			7,272			-
	Retirement and pension cost		758,240			-			816,558			-			7,929			-
	Allowance for doubtful accounts		66,170			-			48,885			-			475			-
	Depreciation		48,315			-			-			-			-			-
	Net loss on other investments		285,505			-			240,698			-			2,337			-
	Operating loss carryforwards		1,416,522			-			1,370,277			-			13,306			-
	Transactions in transit*		-			47,983			-			86,953			-			845
	Impairment loss on telephone rights		77,101			-			77,690			-			755			-
	Accrued enterprise tax		179,725			-			101,252			-			983			-
	Asset retirement obligation		120,116			-			184,325			-			1,790			-
	Deferred revenue		468,382			-			614,054			-			5,963			-
	Customer relationship		-			1,690,781			-			1,505,159			-			14,616
	Tax deduction of goodwill		-			528,299			-			690,499			-			6,705
	Excess of tax deductible goodwill over the reported amount of goodwill		570,356			-			316,818			-			3,077			-
	Trademark		-			38,413			-			38,413			-			373
	Investments in equity method investees		-			168,061			-			233,550			-			2,268
	Other		237,761			159,753			217,213			166,346			2,109			1,615
	Total		5,014,984			2,923,913			4,843,452			3,567,953			47,033			34,647
	Valuation allowance		(1,361,807	)		-			(428,184	)		-			(4,158	)		-
	Total	¥	3,653,177		¥	2,923,913		¥	4,415,268		¥	3,567,953		$	42,875		$	34,647
Schedule of Unrecognized Tax Benefits Roll Forward [Table Text Block]	'
		Thousands of Yen
	Year Ending	Enterprise Tax			Inhabitant Tax			Others
	31-Mar	Subject to			Subject to
		Consolidation Tax			Consolidation Tax
		Filing			Filing
	2015		-			-			-
	2016		-			-			-
	2017		-			-			-
	2018	¥	38,120		¥	10,762		¥	411,351
	2019 and thereafter		221,664			62,745			3,339,609
	Total	¥	259,784		¥	73,507		¥	3,750,960
		Thousands of U.S. Dollars
	Year Ending	Enterprise Tax			Inhabitant Tax			Others
	31-Mar	Subject to			Subject to
		Consolidation Tax			Consolidation Tax
		Filing			Filing
	2015		-			-			-
	2016		-			-			-
	2017		-			-			-
	2018	$	370		$	105		$	3,994
	2019 and thereafter		2,153			609			32,430
	Total	$	2,523		$	714		$	36,424
Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]	'
		Thousands of Yen									Thousands of
											U.S. Dollars
		2012			2013			2014			2014
	Amount computed by using normal Japanese statutory tax rate	¥	2,450,250		¥	2,970,879		¥	2,403,283		$	23,337
	Increase (decrease) in taxes resulting from:
	Expenses not deductible for tax purpose		81,115			89,012			102,634			997
	Inhabitant tax―per capita		34,415			35,809			37,122			360
	Expiration of operating loss carryforward		176,829			-			-			-
	Change in valuation allowance		(107,171	)		(666,973	)		(957,182	)		(9,295	)
	Tax effects on investments in equity method investees		-			168,061			65,489			636
	Enterprise tax―not based on income		68,960			77,868			82,191			798
	Tax rate change		(110,381	)		-			106,487			1,034
	Other—net		(68,531	)		(67,074	)		(44,719	)		(434	)
	Income tax expense as reported	¥	2,525,486		¥	2,607,582		¥	1,795,305		$	17,433

Note_13_Retirement_and_Pension1

Note 13 - Retirement and Pension Plans (Tables)	12 Months Ended
	Mar. 31, 2014
Note 13 - Retirement and Pension Plans (Tables) [Line Items]	'
Schedule of Net Benefit Costs [Table Text Block]	'
		Thousands of Yen									Thousands of
											U.S. Dollars
		2012			2013			2014			2014
	Service cost	¥	467,583		¥	479,158		¥	542,584		$	5,269
	Interest cost		48,335			46,975			45,418			441
	Expected return on plan assets		(27,086	)		(29,796	)		(48,303	)		(470	)
	Amortization of transition obligation		369			369			369			4
	Other		(12,632	)		-			-			-
	Net periodic pension cost	¥	476,569		¥	496,706		¥	540,068		$	5,244
Schedule of Defined Benefit Plan Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block]	'
		Thousands of Yen									Thousands of
											U.S. Dollars
		2012			2013			2014			2014
	Net actuarial loss (gain)	¥	39,083		¥	92,808		¥	(63,775	)	$	(619	)
	Amortization of transition obligation in net periodic pension cost		(369	)		(369	)		(369	)		(4	)
	Other		12,632			-			-			-
	Amounts recognized in other comprehensive income (loss)	¥	51,346		¥	92,439		¥	(64,144	)	$	(623	)
	Total net periodic pension cost and amounts recognized in other comprehensive income	¥	527,915		¥	589,145		¥	475,924		$	4,621
Changes in Projected Benefit Obligations, Fair Value of Plan Assets, and Funded Status of Plan [Table Text Block]	'
		Thousands of Yen						Thousands of
								U.S. Dollars
		2013			2014			2014
	Change in benefit obligation:
	Benefit obligation at beginning of year	¥	3,196,857		¥	3,855,332		$	37,438
	Service cost		479,158			542,584			5,269
	Interest cost		46,975			45,418			441
	Actuarial loss		209,406			17,098			166
	Benefit paid		(77,064	)		(33,834	)		(329	)
	Benefit obligation at end of year		3,855,332			4,426,598			42,985
	Change in plan assets:
	Fair value of plan assets at beginning of year		1,655,373			2,012,611			19,544
	Actual return on plan assets		146,394			129,176			1,254
	Employer contribution		257,288			296,631			2,880
	Benefits paid		(46,444	)		(13,919	)		(135	)
	Fair value of plan assets at end of year		2,012,611			2,424,499			23,543
	Funded status at end of year	¥	(1,842,721	)	¥	(2,002,099	)	$	(19,442	)
Schedule of Amounts Recognized in Balance Sheet [Table Text Block]	'
		Thousands of Yen						Thousands of
								U.S. Dollars
		2013			2014			2014
	Accrued retirement and pension costs―noncurrent	¥	(1,842,721	)	¥	(2,002,099	)	$	(19,442	)
	Net amount recognized	¥	(1,842,721	)	¥	(2,002,099	)	$	(19,442	)
Schedule of Amounts Recognized in Other Comprehensive Income (Loss) [Table Text Block]	'
		Thousands of Yen						Thousands of
								U.S. Dollars
		2013			2014			2014
	Net actuarial loss	¥	305,049		¥	241,275		$	2,343
	Obligation at transition		1,104			734			7
	Total	¥	306,153		¥	242,009		$	2,350
Schedule of Assumptions Used [Table Text Block]	'
		Benefit						Net Periodic Costs
		Obligations
		2013			2014			2012			2013			2014
	Discount rate		1.2	%		1.7	%		1.8	%		1.5	%		1.2	%
	Expected long-term rate of return on plan assets								1.9			1.8			2.4
	Rate of increase in compensation		3.3			3.2			3.4			3.3			3.3
Schedule of Expected Benefit Payments [Table Text Block]	'
	Years Ending	Thousands of Yen			Thousands of
	31-Mar				U.S. Dollars
	2015	¥	64,015		$	622
	2016		75,530			734
	2017		99,316			964
	2018		123,816			1,202
	2019		134,463			1,306
	2020－2024		1,279,018			12,420
	Total	¥	1,776,158		$	17,248
Fair Value, Assets Measured on Recurring Basis [Table Text Block]	'
		Thousands of Yen
											Total
		Level 1			Level 2			Level 3			2013
	31-Mar-13
	Assets―
	Available-for-sale securities―equity securities	¥	1,309,923			-			-		¥	1,309,923
		Thousands of Yen
											Total
	31-Mar-14	Level 1			Level 2			Level 3			2014
	Assets―
	Available-for-sale securities―equity  securities	¥	3,751,011			-			-		¥	3,751,011
United States of America, Dollars	'
Note 13 - Retirement and Pension Plans (Tables) [Line Items]	'
Fair Value, Assets Measured on Recurring Basis [Table Text Block]	'
	Basis of Fair Value Measurement of Pension Plan Assets at March 31, 2014	Thousands of U.S. Dollars
		Level 1			Level 2			Level 3			Total
	Equity securities:
	Japanese equity	$	3,387			-			-		$	3,387
	U.S. equity		867			-			-			867
	Other equity―developed countries		597			-			-			597
	Total equity securities		4,851			-			-			4,851
	Debt securities:
	Japanese government and municipalities		-		$	4,722			-			4,722
	Japanese corporate bonds―investment grade		-			1,593			-			1,593
	U.S. government		-			635			-			635
	Other government―developed countries		-			1,474			-			1,474
	Residential mortgage-backed		-			188			-			188
	Total debt securities		-			8,612			-			8,612
	Other financial instruments*		-			9,225			-			9,225
	Cash		855			-			-			855
	Total assets at fair value	$	5,706		$	17,837			-		$	23,543
Pension Plan, Defined Benefit [Member]	'
Note 13 - Retirement and Pension Plans (Tables) [Line Items]	'
Fair Value, Assets Measured on Recurring Basis [Table Text Block]	'
	Basis of Fair Value Measurement of Pension Plan Assets at March 31, 2013	Thousands of Yen
		Level 1			Level 2			Level 3			Total
	Equity securities:
	Japanese equity	¥	302,533			-			-		¥	302,533
	U.S. equity		72,760			-			-			72,760
	Other equity―developed countries		51,220			-			-			51,220
	Total equity securities		426,513			-			-			426,513
	Debt securities:
	Japanese government and municipalities		-		¥	477,430			-			477,430
	Japanese corporate bonds―investment grade		-			59,533			-			59,533
	U.S. government		-			74,294			-			74,294
	Other government―developed countries		-			103,471			-			103,471
	Residential mortgage-backed		-			26,252			-			26,252
	Total debt securities		-			740,980			-			740,980
	Other financial instruments*		-			800,968			-			800,968
	Cash		44,150			-			-			44,150
	Total assets at fair value	¥	470,663		¥	1,541,948			-		¥	2,012,611
	Basis of Fair Value Measurement of Pension Plan Assets at March 31, 2014	Thousands of Yen
		Level 1			Level 2			Level 3			Total
	Equity securities:
	Japanese equity	¥	348,758			-			-		¥	348,758
	U.S. equity		89,304			-			-			89,304
	Other equity― developed countries		61,498			-			-			61,498
	Total equity securities		499,560			-			-			499,560
	Debt securities:
	Japanese government and municipalities		-		¥	486,308			-			486,308
	Japanese corporate bonds― investment grade		-			164,037			-			164,037
	U.S. government		-			65,339			-			65,339
	Other government― developed countries		-			151,824			-			151,824
	Residential mortgage-backed		-			19,337			-			19,337
	Total debt securities		-			886,845			-			886,845
	Other financial instruments*		-			950,011			-			950,011
	Cash		88,083			-			-			88,083
	Total assets at fair value	¥	587,643		¥	1,836,856			-		¥	2,424,499

Note_14_Shareholders_Equity_Ta

Note 14 - Shareholders' Equity (Tables)	12 Months Ended
	Mar. 31, 2014
Stockholders' Equity Note [Abstract]	'
Schedule of Share-based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions [Table Text Block]	'
		2012			2013			2014
	Assumptions:
	Risk-free interest rate		1.614	%		1.298	%		1.314	%
	Expected lives (years)		15			15			15
	Expected volatility		59.892	%		57.02	%		55.861	%
	Expected dividends		0.924	%		0.893	%		0.535	%
Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]	'
								Yen			Years		Thousands		Thousands
													of Yen		of U.S.
															Dollars
		Number			Number			Exercise			Remaining		Total		Total
		of Options			of Shares			Price			Life		Intrinsic		Intrinsic
													Value		Value
	Unexercised options outstanding—March 31, 2012		138			27,600			1
	Granted		130			26,000			1
	Exercised		-			-			-
	Forfeited or expired		-			-			-
	Unexercised options outstanding—March 31, 2013		268			53,600			1
	Granted		89			17,800			1
	Exercised		11			2,200			1
	Forfeited or expired		-			-			-
	Unexercised options outstanding—March 31, 2014		346			69,200			1
	Exercisable options—March 31, 2014		257			51,400			1			27.79	¥	127,523	$	1,238
	Expected to vest after July 10, 2014		89			17,800			1			29.28	¥	44,162	$	429
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Table Text Block]	'
		Thousands of Yen									Thousands of
											U.S. Dollars
		2012			2013			2014			2014
	Net income attributable to IIJ	¥	3,640,963		¥	5,300,654		¥	4,442,237		$	43,137
	Transfers (to) from the noncontrolling interests
	Decrease in additional paid-in capital for purchase of GDX common shares		(85,437	)		-			-			-
	Increase in additional paid-in capital for acquisition of noncontrolling interest of IIJ-Exlayer		-			-			99			1
	Net transfers (to) from noncontrolling interest		(85,437	)		-			99			1
	Change from net income attributable to IIJ and transfers (to) from noncontrolling interests	¥	3,555,526		¥	5,300,654		¥	4,442,336		$	43,138

Note_15_Other_Comprehensive_In1

Note 15 - Other Comprehensive Income (Loss) (Tables)	12 Months Ended
	Mar. 31, 2014
Note 15 - Other Comprehensive Income (Loss) (Tables) [Line Items]	'
Comprehensive Income (Loss) [Table Text Block]	'
		Thousands of Yen
		Before Tax			Tax (Expense)			Net of Tax
		Amount			Benefit			Amount
	Year ended March 31, 2012:
	Foreign currency translation adjustments	¥	(9,539	)		-		¥	(9,539	)
	Unrealized holding gain (loss) on securities:
	Amount arising during the period		56,384		¥	(20,242	)		36,142
	Less:  Reclassification adjustments for losses included in net income		91,064			(37,336	)		53,728
	Other		-			12,875			12,875
	Net unrealized holding gain (loss) during the period		147,448			(44,703	)		102,745
	Defined benefit pension plans:
	Amount arising during the period		(39,083	)		14,030			(25,053	)
	Less: Reclassification adjustments for gains included in net income		(12,263	)		5,711			(6,552	)
	Net defined benefit pension plans		(51,346	)		19,741			(31,605	)
	Other comprehensive income (loss)	¥	86,563		¥	(24,962	)	¥	61,601
	Year ended March 31, 2013:
	Foreign currency translation adjustments	¥	90,014			-		¥	90,014
	Unrealized holding gain (loss) on securities:
	Amount arising during the period		380,637		¥	(136,649	)		243,988
	Less:  Reclassification adjustments for losses included in net income		19,788			(7,579	)		12,209
	Other		-			324			324
	Net unrealized holding gain (loss) during the period		400,425			(143,904	)		256,521
	Defined benefit pension plans:
	Amount arising during the period		(92,808	)		33,319			(59,489	)
	Less: Reclassification adjustments for losses included in net income		369			(132	)		237
	Net defined benefit pension plans		(92,439	)		33,187			(59,252	)
	Other comprehensive income (loss)	¥	398,000		¥	(110,717	)	¥	287,283
		Thousands of Yen
		Before Tax			Tax (Expense)			Net of Tax
		Amount			Benefit			Amount
	Year ended March 31, 2014:
	Foreign currency translation adjustments	¥	419,557			-		¥	419,557
	Unrealized holding gain (loss) on securities:
	Amount arising during the period		1,656,759		¥	(594,776	)		1,061,983
	Less: Reclassification adjustments for gains included in net income		(107,655	)		41,232			(66,423	)
	Other		-			(7,421	)		(7,421	)
	Net unrealized holding gain (loss) during the period		1,549,104			(560,965	)		988,139
	Defined benefit pension plans:
	Amount arising during the period		63,775			(22,896	)		40,879
	Less: Reclassification adjustments for losses included in net income		369			(133	)		236
	Net defined benefit pension plans		64,144			(23,029	)		41,115
	Other comprehensive income (loss)	¥	2,032,805		¥	(583,994	)	¥	1,448,811
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	'
		Thousands of Yen
		Unrealized holding			Defined benefit			Foreign currency			Total
		gain on securities			pension plans			translation
								adjustments
	Year ended March 31, 2013:	¥	495,217		¥	(187,318	)	¥	(44,129	)	¥	263,770
	Other comprehensive income before reclassifications		1,054,562			40,879			419,701			1,515,142
	Amounts reclassified out of accumulated other comprehensive income		(66,423	)		236			―			(66,187	)
	Other comprehensive income		988,139			41,115			419,701			1,448,955
	Other		―			―			61			61
	Year ended March 31, 2014:	¥	1,483,356		¥	(146,203	)	¥	375,633		¥	1,712,786
Reclassified Accumulted Other Comprehensive Income [Table Text Block]	'
		Thousands of Yen			Thousands of
					U.S. Dollars
		2014			2014
	Comprehensive income components:							Location
	Unrealized holding gain on securities	¥	107,655		$	1,045		Net gain on sales of other investments
			(41,232	)		(400	)	Income tax expense
			66,423			645		Net income
	Defined benefit pension plans		(369	)		(4	)	Net periodic pension costs (Note 13)
			133			2		Income tax expense
			(236	)		(2	)	Net income
	Total amount reclassified	¥	66,187		$	643
United States of America, Dollars	'
Note 15 - Other Comprehensive Income (Loss) (Tables) [Line Items]	'
Comprehensive Income (Loss) [Table Text Block]	'
		Thousands of U.S. Dollars
		Before Tax			Tax (Expense)			Net of Tax
		Amount			Benefit			Amount
	Year ended March 31, 2014:
	Foreign currency translation adjustments	$	4,074			-		$	4,074
	Unrealized holding gain (loss) on securities:
	Amount arising during the period		16,088		$	(5,776	)		10,312
	Less: Reclassification adjustments for gains included in net income		(1,045	)		400			(645	)
	Other		-			(71	)		(71	)
	Net unrealized holding gain (loss) during the period		15,043			(5,447	)		9,596
	Defined benefit pension plans:
	Amount arising during the period		619			(222	)		397
	Less: Reclassification adjustments for gains included in net income		4			(2	)		2
	Net defined benefit pension plans		623			(224	)		399
	Other comprehensive income (loss)	$	19,740		$	(5,671	)	$	14,069
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	'
		Thousands of U.S. Dollars
		Unrealized holding			Defined benefit			Foreign currency			Total
		gain on securities			pension plans			translation
								adjustments
	Year ended March 31, 2013:	$	4,809		$	(1,820	)	$	(428	)	$	2,561
	Other comprehensive income before reclassifications		10,241			397			4,075			14,713
	Amounts reclassified out of accumulated other comprehensive income		(645	)		2			―			(643	)
	Other comprehensive income		9,596			399			4,075			14,070
	Other		―			―			1			1
	Year ended March 31, 2014:	$	14,405		$	(1,421	)	$	3,648		$	16,632

Note_16_Basic_and_Diluted_Net_1

Note 16 - Basic and Diluted Net Income Per Common Share (Tables)	12 Months Ended
	Mar. 31, 2014
Note 16 - Basic and Diluted Net Income Per Common Share (Tables) [Line Items]	'
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	'
		Yen						U.S. Dollars
		2012		2013		2014		2014
	Basic net income attributable to Internet Initiative Japan Inc. per common share	¥	89.82	¥	130.76	¥	100.26	$	0.97
	Diluted net income attributable to Internet Initiative Japan Inc. per common share	¥	89.78	¥	130.65	¥	100.14	$	0.97
Numerator [Member]	'
Note 16 - Basic and Diluted Net Income Per Common Share (Tables) [Line Items]	'
Schedule of Earnings Per Share Calculation [Table Text Block]	'
		Thousands of Yen						Thousands of
								U.S. Dollars
		2012		2013		2014		2014
	Numerator―
	Net income attributable to Internet Initiative Japan Inc.―basic and diluted	¥	3,640,963	¥	5,300,654	¥	4,442,237	$	43,137
Denominator [Member]	'
Note 16 - Basic and Diluted Net Income Per Common Share (Tables) [Line Items]	'
Schedule of Earnings Per Share Calculation [Table Text Block]	'
		Number of Shares
		2012		2013		2014
	Denominator:
	Weighted-average common shares outstanding―basic		40,536,800		40,536,800		44,306,680
	Dilutive effect of stock options		19,600		35,800		54,403
	Weighted-average common shares outstanding―diluted		40,556,400		40,572,600		44,361,083

Note_18_Financial_Instruments_

Note 18 - Financial Instruments (Tables)	12 Months Ended
	Mar. 31, 2014
Disclosure Text Block Supplement [Abstract]	'
Schedule of Financial Assets [Table Text Block]	'
		Thousands of Yen								Thousands of
										U.S. Dollars
		2013				2014				2014
		Carrying		Fair		Carrying		Fair		Carrying		Fair
		Amount		Value		Amount		Value		Amount		Value
	Other investments for which it is:
	Practicable to estimate fair value	¥	1,309,923	¥	1,309,923	¥	3,751,011	¥	3,751,011	$	36,425	$	36,425
	Not practicable		2,461,339		-		2,604,806		-		25,294		-
	Noncurrent refundable insurance policies (other assets)		64,020		64,020		63,062		63,062		612		612

Note_19_Fair_Value_Measurement1

Note 19 - Fair Value Measurements (Tables)	12 Months Ended
	Mar. 31, 2014
Note 19 - Fair Value Measurements (Tables) [Line Items]	'
Fair Value, Assets Measured on Recurring Basis [Table Text Block]	'
		Thousands of Yen
										Total
		Level 1			Level 2			Level 3		2013
	31-Mar-13
	Assets―
	Available-for-sale securities―equity securities	¥	1,309,923			-			-	¥	1,309,923
		Thousands of Yen
										Total
	31-Mar-14	Level 1			Level 2			Level 3		2014
	Assets―
	Available-for-sale securities―equity  securities	¥	3,751,011			-			-	¥	3,751,011
Fair Value Measurements, Nonrecurring [Table Text Block]	'
		Thousands of Yen
	31-Mar-13	Level 1			Level 2			Level 3		Impairment Loss
	Assets:
	Trademark		-			-		¥	107,000	¥	48,000
			-			-		¥	107,000	¥	48,000
Fair Value Inputs, Assets, Quantitative Information [Table Text Block]	'
		Thousands
		of Yen
	31-Mar-13	Fair		Valuation		Unobservable	Range
		value		technique		inputs
	Trademark		¥107,000	Relief from		Discount Rate		7.50%
				royalty method		Royalty rate		0.30%
US Dollars [Member]	'
Note 19 - Fair Value Measurements (Tables) [Line Items]	'
Fair Value, Assets Measured on Recurring Basis [Table Text Block]	'
		Thousands of U.S. Dollars
										Total
	31-Mar-14	Level 1			Level 2			Level 3		2014
	Assets―
	Available-for-sale securities―equity  securities	$	36,425			-			-	$	36,425

Note_20_Business_Segments_Tabl

Note 20 - Business Segments (Tables)	12 Months Ended
	Mar. 31, 2014
Revenues [Member]	'
Note 20 - Business Segments (Tables) [Line Items]	'
Schedule of Segment Reporting Information, by Segment [Table Text Block]	'
		Thousands of Yen							Thousands of
									U.S. Dollars
		2012			2013		2014		2014
	Network service and systems integration business:
	Customers	¥	95,990,449		¥	103,928,400	¥	111,445,519	$	1,082,205
	Intersegment		506,030			558,753		455,975		4,428
	Total		96,496,479			104,487,153		111,901,494		1,086,633
	ATM operation business:
	Customers		1,324,156			2,320,086		2,826,832		27,450
	Intersegment	-			-		-		-
	Total		1,324,156			2,320,086		2,826,832		27,450
	Elimination		506,030			558,753		455,975		4,428
	Consolidated total	¥	97,314,605		¥	106,248,486	¥	114,272,351	$	1,109,655
Profit Or Loss [Member]	'
Note 20 - Business Segments (Tables) [Line Items]	'
Schedule of Segment Reporting Information, by Segment [Table Text Block]	'
		Thousands of Yen							Thousands of
									U.S. Dollars
		2012			2013		2014		2014
	Operating income (loss):
	Network service and systems integration business	¥	6,631,476		¥	7,629,435	¥	5,274,753	$	51,221
	ATM operation business		(194,264	)		239,035		578,794		5,620
	Elimination		83,729			115,828		130,235		1,264
	Consolidated total	¥	6,353,483		¥	7,752,642	¥	5,723,312	$	55,577
Segment Assets [Member]	'
Note 20 - Business Segments (Tables) [Line Items]	'
Schedule of Segment Reporting Information, by Segment [Table Text Block]	'
		Thousands of Yen					Thousands of
							U.S. Dollars
		2013			2014		2014
	Segment assets:
	Network service and systems integration business	¥	79,958,814		¥	100,860,325	$	979,417
	ATM operation business		2,152,452			3,006,250		29,192
	Elimination
	Consolidated total	¥	82,111,266		¥	103,866,575	$	1,008,609
Corporate and Other [Member]	'
Note 20 - Business Segments (Tables) [Line Items]	'
Schedule of Segment Reporting Information, by Segment [Table Text Block]	'
		Thousands of Yen							Thousands of
									U.S. Dollars
		2012			2013		2014		2014
	Depreciation and amortization:
	Network service and systems integration business	¥	7,006,576		¥	7,178,397	¥	8,405,080	$	81,619
	ATM operation business		137,055			329,411		417,901		4,058
	Consolidated total	¥	7,143,631		¥	7,507,808	¥	8,822,981	$	85,677

Note_22_Related_Party_Transact1

Note 22 - Related Party Transactions (Tables)	12 Months Ended
	Mar. 31, 2014
Related Party Transactions [Abstract]	'
Schedule of Related Party Transactions [Table Text Block]	'
		Thousands of Yen						Thousands of
								U.S. Dollars
		2012		2013		2014		2014
	Accounts receivable		-	¥	171,909	¥	446,857	$	4,339
	Accounts payable		-		1,578,969		1,822,997		17,702
	Revenues	¥	895,189		880,079		2,370,954		23,023
	Costs		14,225,717		14,966,177		15,579,173		151,283

Note_1_Description_of_Business2

Note 1 - Description of Business and Summary of Significant Accounting Policies (Details)	0 Months Ended	12 Months Ended			0 Months Ended	6 Months Ended	0 Months Ended	6 Months Ended	12 Months Ended
	Oct. 01, 2012	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2013	Sep. 06, 2012	Oct. 01, 2012	Sep. 06, 2012	Oct. 01, 2012	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014
			Japan, Yen	United States of America, Dollars	Denominator [Member]	Denominator [Member]	Numerator [Member]	Numerator [Member]	Software and Software Development Costs [Member]	Minimum [Member]	Maximum [Member]
Note 1 - Description of Business and Summary of Significant Accounting Policies (Details) [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Percentage Of Voting Shares Owned By NTT Group	'	26.40%	'	'	'	'	'	'	'	'	'
Foreign Currency Exchange Rate, Translation	'	'	102.98	1	'	'	'	'	'	'	'
Systems Operation And Maintenance Contract Period	'	'	'	'	'	'	'	'	'	'1 year	'5 years
Finite-Lived Intangible Asset, Useful Life	'	'	'	'	'	'	'	'	'	'6 years	'19 years
Stockholders' Equity Note, Stock Split, Conversion Ratio	200	'	'	'	200	200	1	1	'	'	'
Property, Plant and Equipment, Useful Life	'	'	'	'	'	'	'	'	'5 years	'	'
Number of Operating Segments	'	2	'	'	'	'	'	'	'	'	'

Note_1_Description_of_Business3

Note 1 - Description of Business and Summary of Significant Accounting Policies (Details) - Useful Lives for Depreciation and Amortization by Major Asset Classes	12 Months Ended
	Mar. 31, 2014
Equipment [Member] | Minimum [Member]	'
Note 1 - Description of Business and Summary of Significant Accounting Policies (Details) - Useful Lives for Depreciation and Amortization by Major Asset Classes [Line Items]	'
Property, plant and equipment, useful lives	'3 years
Equipment [Member] | Maximum [Member]	'
Note 1 - Description of Business and Summary of Significant Accounting Policies (Details) - Useful Lives for Depreciation and Amortization by Major Asset Classes [Line Items]	'
Property, plant and equipment, useful lives	'20 years
Building [Member]	'
Note 1 - Description of Business and Summary of Significant Accounting Policies (Details) - Useful Lives for Depreciation and Amortization by Major Asset Classes [Line Items]	'
Property, plant and equipment, useful lives	'20 years
Leasehold Improvements [Member] | Minimum [Member]	'
Note 1 - Description of Business and Summary of Significant Accounting Policies (Details) - Useful Lives for Depreciation and Amortization by Major Asset Classes [Line Items]	'
Property, plant and equipment, useful lives	'8 years
Leasehold Improvements [Member] | Maximum [Member]	'
Note 1 - Description of Business and Summary of Significant Accounting Policies (Details) - Useful Lives for Depreciation and Amortization by Major Asset Classes [Line Items]	'
Property, plant and equipment, useful lives	'20 years
Software and Software Development Costs [Member]	'
Note 1 - Description of Business and Summary of Significant Accounting Policies (Details) - Useful Lives for Depreciation and Amortization by Major Asset Classes [Line Items]	'
Property, plant and equipment, useful lives	'5 years
Assets Held under Capital Leases [Member] | Minimum [Member]	'
Note 1 - Description of Business and Summary of Significant Accounting Policies (Details) - Useful Lives for Depreciation and Amortization by Major Asset Classes [Line Items]	'
Property, plant and equipment, useful lives	'4 years
Assets Held under Capital Leases [Member] | Maximum [Member]	'
Note 1 - Description of Business and Summary of Significant Accounting Policies (Details) - Useful Lives for Depreciation and Amortization by Major Asset Classes [Line Items]	'
Property, plant and equipment, useful lives	'6 years

Note_2_Business_Combinations_D

Note 2 - Business Combinations (Details)	12 Months Ended		0 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2012	Apr. 02, 2012	Apr. 02, 2012
			IIJ-Exlayer [Member]	IIJ-Exlayer [Member]
			USD ($)	JPY (¥)
Note 2 - Business Combinations (Details) [Line Items]	'	'	'	'
Business Acquisition, Percentage of Voting Interests Acquired	'	'	99.90%	99.90%
Business Combination, Consideration Transferred	'	'	$3,183	¥ 299,700
Number of Businesses Acquired	0	0	'	'

Note_3_Inventory_Details_The_C

Note 3 - Inventory (Details) - The Components of Inventories	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013
In Thousands, unless otherwise specified	USD ($)	JPY (¥)	JPY (¥)
The Components of Inventories [Abstract]	'	'	'
Network equipment purchased for resale	$4,888	¥ 503,334	¥ 350,976
Work in process	11,331	1,166,924	950,708
Total inventories	$16,219	¥ 1,670,258	¥ 1,301,684

Note_4_Other_Investments_Detai

Note 4 - Other Investments (Details)	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2014	Mar. 31, 2014
	USD ($)	JPY (¥)	JPY (¥)	JPY (¥)	Company 1 [Member]	Company 2 [Member]
Note 4 - Other Investments (Details) [Line Items]	'	'	'	'	'	'
Investment Fair Value Percentage Below Cost	'	'	'	'	0.60%	13.40%
Proceeds from Sale of Available-for-sale Securities	$3,805,000	¥ 391,814,000	¥ 0	¥ 226,346,000	'	'
Available-for-sale Securities, Gross Realized Gains	1,045,000	107,655,000	'	9,140,000	'	'
Available-for-sale Securities, Gross Realized Losses	'	'	'	12,293,000	'	'
Realized Investment Gains (Losses)	3,043,000	313,393,000	'	'	'	'
Cost Method Investments	25,294,000	2,604,806,000	2,461,339,000	'	'	'
Other than Temporary Impairment Losses, Investments, Available-for-sale Securities	'	'	19,788,000	87,911,000	'	'
Cost-method Investments, Other than Temporary Impairment	'	'	¥ 0	¥ 71,681,000	'	'

Note_4_Other_Investments_Detai1

Note 4 - Other Investments (Details) - Securities Classified as Available-for-Sale in Yen	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013
	USD ($)	JPY (¥)	JPY (¥)
Securities Classified as Available-for-Sale in Yen [Abstract]	'	'	'
Available-for-sale—Cost	$13,515	¥ 1,391,820	¥ 500,616
Available-for-sale—Unrealized Gains	22,961	2,364,442	813,445
Available-for-sale—Unrealized Losses	51	5,251	4,138
Available-for-sale—Fair Value	$36,425	¥ 3,751,011	¥ 1,309,923

Note_4_Other_Investments_Detai2

Note 4 - Other Investments (Details) - Securities Classified as Available-for-Sale in US Dollars	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013
	USD ($)	JPY (¥)	JPY (¥)
Securities Classified as Available-for-Sale in US Dollars [Abstract]	'	'	'
Available-for-sale—Equity securities	$13,515	¥ 1,391,820	¥ 500,616
Available-for-sale—Equity securities	22,961	2,364,442	813,445
Available-for-sale—Equity securities	51	5,251	4,138
Available-for-sale—Equity securities	$36,425	¥ 3,751,011	¥ 1,309,923

Note_4_Other_Investments_Detai3

Note 4 - Other Investments (Details) - Securities Classified as Available-for-Sale that have been in a Continuous Unrealized Loss Position in Yen	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013
	USD ($)	JPY (¥)	JPY (¥)
Securities Classified as Available-for-Sale that have been in a Continuous Unrealized Loss Position in Yen [Abstract]	'	'	'
Available-for-sale—Fair Value Less than 12 Months	$549	¥ 56,524	¥ 27,902
Available-for-sale—Unrealized Losses Less than 12 Months	51	5,251	4,138
Available-for-sale—Fair Value	549	56,524	27,902
Available-for-sale—Unrealized Losses	$51	¥ 5,251	¥ 4,138

Note_4_Other_Investments_Detai4

Note 4 - Other Investments (Details) - Securities Classified as Available-for-Sale that have been in a Continuous Unrealized Loss Position in US Dollars	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013
	USD ($)	JPY (¥)	JPY (¥)
Securities Classified as Available-for-Sale that have been in a Continuous Unrealized Loss Position in US Dollars [Abstract]	'	'	'
Available-for-sale—Equity securities	$549	¥ 56,524	¥ 27,902
Available-for-sale—Equity securities	51	5,251	4,138
Available-for-sale—Equity securities	549	56,524	27,902
Available-for-sale—Equity securities	$51	¥ 5,251	¥ 4,138

Note_5_Allowance_for_Doubtful_2

Note 5 - Allowance for Doubtful Accounts and Loans (Details) - Analysis of Allowance for Doubtful Accounts and Loans in Yen	0 Months Ended			12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
	JPY (¥)	JPY (¥)	JPY (¥)	USD ($)	JPY (¥)	JPY (¥)	JPY (¥)
Analysis of Allowance for Doubtful Accounts and Loans in Yen [Abstract]	'	'	'	'	'	'	'
Balance at Beginning of Year	¥ 176,393	¥ 205,039	¥ 142,871	$1,713	¥ 176,393	¥ 205,039	'
Credits Charged Off	-12,067	-17,934	-19,878	-117	'	'	'
Provision for (Reversal of) Doubtful Accounts	-46,935	-10,712	82,046	-456	-46,935	-10,712	82,046
Balance at End of Year	'	'	'	$1,140	¥ 117,391	¥ 176,393	¥ 205,039

Note_5_Allowance_for_Doubtful_3

Note 5 - Allowance for Doubtful Accounts and Loans (Details) - Analysis of Allowance for Doubtful Accounts and Loans in US Dollars	0 Months Ended			12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012	Mar. 30, 2014	Mar. 31, 2013	Mar. 30, 2013	Mar. 30, 2012
	JPY (¥)	JPY (¥)	JPY (¥)	USD ($)	JPY (¥)	JPY (¥)	JPY (¥)	JPY (¥)	USD ($)	JPY (¥)	JPY (¥)
Analysis of Allowance for Doubtful Accounts and Loans in US Dollars [Abstract]	'	'	'	'	'	'	'	'	'	'	'
Year ended March 31, 2014	'	'	'	$1,140	¥ 117,391	¥ 176,393	¥ 205,039	¥ 176,393	$1,713	¥ 205,039	¥ 142,871
Year ended March 31, 2014	-12,067	-17,934	-19,878	-117	'	'	'	'	'	'	'
Year ended March 31, 2014	¥ (46,935)	¥ (10,712)	¥ 82,046	($456)	¥ (46,935)	¥ (10,712)	¥ 82,046	'	'	'	'

Note_6_Investments_in_Equity_M2

Note 6 - Investments in Equity Method Investees (Details)	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014
	USD ($)	JPY (¥)	JPY (¥)	JPY (¥)	Appiaries [Member]	Appiaries [Member]	Stratosphere [Member]	Stratosphere [Member]	Equity Method Investee [Member]	Equity Method Investee [Member]
					USD ($)	JPY (¥)	Other Assets [Member]	Other Assets [Member]	USD ($)	JPY (¥)
							USD ($)	JPY (¥)
Note 6 - Investments in Equity Method Investees (Details) [Line Items]	'	'	'	'	'	'	'	'	'	'
Notes, Loans and Financing Receivable, Net, Noncurrent	'	'	'	'	'	'	$194	¥ 20,000	'	'
Payments to Acquire Equity Method Investments	1,941	199,920	100,000	24,647	1,941	199,920	'	'	'	'
Equity Method Investment, Summarized Financial Information, Assets	'	'	'	'	'	'	'	'	$523	¥ 53,841

Note_6_Investments_in_Equity_M3

Note 6 - Investments in Equity Method Investees (Details) - Balances Associated with Equity Method Investees	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
	USD ($)	JPY (¥)	JPY (¥)	JPY (¥)	Equity Method Investments [Member]	Equity Method Investments [Member]	Equity Method Investments [Member]	Equity Method Investments [Member]
					USD ($)	JPY (¥)	JPY (¥)	JPY (¥)
Related Party Transaction [Line Items]	'	'	'	'	'	'	'	'
Accounts receivable	'	'	'	'	$419	¥ 43,170	¥ 52,422	'
Accounts payable	'	'	'	'	394	40,613	39,734	'
Revenues	1,109,655	114,272,351	106,248,486	97,314,605	5,227	538,288	598,765	624,718
Costs and expenses	$1,054,078	¥ 108,549,039	¥ 98,495,844	¥ 90,961,122	$4,383	¥ 451,342	¥ 456,892	¥ 403,400

Note_6_Investments_in_Equity_M4

Note 6 - Investments in Equity Method Investees (Details) - Equity Method Investees and Respective Ownership Percentages

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

In Thousands, unless otherwise specified

USD ($)

JPY (¥)

JPY (¥)

Multifeed [Member]

Multifeed [Member]

Multifeed [Member]

I-Revo [Member]

I-Revo [Member]

I-Revo [Member]

Trinity [Member]

Trinity [Member]

Trinity [Member]

Stratosphere [Member]

Stratosphere [Member]

Stratosphere [Member]

Appiaries [Member]

Appiaries [Member]

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

Schedule of Equity Method Investments [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Equity method percentage

'

'

'

33.00%

33.00%

33.00%

30.00%

30.00%

30.00%

33.75%

33.75%

33.75%

50.00%

50.00%

50.00%

49.00%

49.00%

Equity method investment

$20,253

¥ 2,085,689

¥ 1,681,723

$12,085

¥ 1,244,512

¥ 1,141,909

$5,138

¥ 529,142

¥ 371,888

$862

¥ 88,804

¥ 93,154

$315

¥ 32,451

¥ 74,772

$1,853

¥ 190,780

Note_7_Property_and_Equipment_1

Note 7 - Property and Equipment (Details)	12 Months Ended							12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
	USD ($)	JPY (¥)	JPY (¥)	JPY (¥)	Software Development [Member]	Software Development [Member]	Software Development [Member]	Software To Be Leased [Member]	Software To Be Leased [Member]	Software To Be Leased [Member]	Software To Be Leased [Member]
					USD ($)	JPY (¥)	JPY (¥)	USD ($)	JPY (¥)	JPY (¥)	JPY (¥)
Note 7 - Property and Equipment (Details) [Line Items]	'	'	'	'	'	'	'	'	'	'	'
Depreciation, Depletion and Amortization, Nonproduction	$81,180	¥ 8,359,907	¥ 6,950,249	¥ 6,522,033	'	'	'	'	'	'	'
Gain (Loss) on Disposition of Assets	-811	-83,487	-14,638	-62,368	'	'	'	'	'	'	'
Capitalized Computer Software, Gross	'	'	'	'	169,070	17,410,834	15,912,108	34,918	3,595,894	2,553,608	'
Capitalized Computer Software, Net	'	'	'	'	'	'	'	24,591	2,532,335	1,952,450	'
Capitalized Computer Software, Amortization	'	'	'	'	'	'	'	$4,807	¥ 495,050	¥ 349,537	¥ 208,435

Note_7_Property_and_Equipment_2

Note 7 - Property and Equipment (Details) - Property and Equipment

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

In Thousands, unless otherwise specified

USD ($)

JPY (¥)

JPY (¥)

Equipment [Member]

Equipment [Member]

Equipment [Member]

Office Equipment [Member]

Office Equipment [Member]

Office Equipment [Member]

Land [Member]

Land [Member]

Building [Member]

Building [Member]

Building [Member]

Leasehold Improvements [Member]

Leasehold Improvements [Member]

Leasehold Improvements [Member]

Software and Software Development Costs [Member]

Software and Software Development Costs [Member]

Software and Software Development Costs [Member]

Assets Held under Capital Leases [Member]

Assets Held under Capital Leases [Member]

Assets Held under Capital Leases [Member]

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

Property, Plant and Equipment [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Property and equipment

$599,117

¥ 61,697,096

¥ 52,542,149

$84,061

¥ 8,656,572

¥ 6,746,069

$32,782

¥ 3,375,846

¥ 2,130,160

$5,176

¥ 532,997

$15,683

¥ 1,615,081

¥ 668,631

$35,357

¥ 3,641,072

¥ 2,666,584

$203,988

¥ 21,006,728

¥ 18,465,716

$222,070

¥ 22,868,800

¥ 21,864,989

Less accumulated depreciation and amortization

-337,207

-34,725,611

-29,516,394

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Property and equipment—net

$261,910

¥ 26,971,485

¥ 23,025,755

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Note_7_Property_and_Equipment_3

Note 7 - Property and Equipment (Details) - Amortization Expense of Software to be Leased (Software To Be Leased [Member])	Mar. 31, 2014	Mar. 31, 2014
In Thousands, unless otherwise specified	USD ($)	JPY (¥)
Note 7 - Property and Equipment (Details) - Amortization Expense of Software to be Leased [Line Items]	'	'
2015	$6,013	¥ 619,166
2016	6,577	677,298
2017	5,112	526,416
2018	5,087	523,848
2019	$1,802	¥ 185,607

Note_8_Goodwill_and_Other_Inta2

Note 8 - Goodwill and Other Intangible Assets (Details)	12 Months Ended					12 Months Ended			12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2013	Mar. 31, 2012	Apr. 02, 2012	Mar. 31, 2014
	USD ($)	JPY (¥)	JPY (¥)	JPY (¥)	USD ($)	Trademarks [Member]	Trademarks [Member]	IIJ-Exlayer [Member]	Weighted Average [Member]
						JPY (¥)	JPY (¥)	JPY (¥)
Note 8 - Goodwill and Other Intangible Assets (Details) [Line Items]	'	'	'	'	'	'	'	'	'
Finite-Lived Intangible Asset, Useful Life	'	'	'	'	'	'	'	'	'15 years 219 days
Amortization of Intangible Assets	$4,497	¥ 463,074	¥ 557,559	'	'	'	'	'	'
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)	'	'	'	'	'	48,000	37,000	'	'
Goodwill, Impairment Loss	'	0	0	0	'	'	'	'	'
Goodwill	$57,972	¥ 5,969,951	¥ 5,969,951	¥ 5,788,333	$57,972	'	'	¥ 181,618	'

Note_8_Goodwill_and_Other_Inta3

Note 8 - Goodwill and Other Intangible Assets (Details) - Components of Intangible Assets	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013
In Thousands, unless otherwise specified	USD ($)	JPY (¥)	USD ($)	JPY (¥)	JPY (¥)	Customer Relationships [Member]	Customer Relationships [Member]	Customer Relationships [Member]
						USD ($)	JPY (¥)	JPY (¥)
Intangible assets subject to amortization:	'	'	'	'	'	'	'	'
Intangible assets subject to amortization	$62,386	¥ 6,424,471	'	¥ 6,424,471	'	$62,386	¥ 6,424,471	¥ 6,424,471
Accumulated amortization	-21,582	-2,222,514	'	-1,759,440	'	-21,582	-2,222,514	-1,759,440
Intangible assets subject to amortization—net	40,804	4,201,957	'	4,665,031	'	'	'	'
Intangible assets not subject to amortization:	'	'	'	'	'	'	'	'
Telephone rights	291	29,987	'	19,400	'	'	'	'
Trademark	1,039	107,000	'	107,000	'	'	'	'
Goodwill	57,972	5,969,951	57,972	5,969,951	5,788,333	'	'	'
Total	59,302	6,106,938	'	6,096,351	'	'	'	'
Total intangible assets	$100,106	¥ 10,308,895	'	¥ 10,761,382	'	'	'	'

Note_8_Goodwill_and_Other_Inta4

Note 8 - Goodwill and Other Intangible Assets (Details) - Estimated Aggregate Amortization Expense of Intangible Assets	Mar. 31, 2014	Mar. 31, 2014
In Thousands, unless otherwise specified	USD ($)	JPY (¥)
Estimated Aggregate Amortization Expense of Intangible Assets [Abstract]	'	'
2015	$3,855	¥ 397,031
2016	3,768	388,014
2017	3,695	380,496
2018	3,549	365,460
2019	$3,451	¥ 355,410

Note_8_Goodwill_and_Other_Inta5

Note 8 - Goodwill and Other Intangible Assets (Details) - Carrying Amount of Goodwill

12 Months Ended

12 Months Ended

In Thousands, unless otherwise specified

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2013

Mar. 31, 2012

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

Network Service and Systems Integration Business [Member]

Network Service and Systems Integration Business [Member]

Network Service and Systems Integration Business [Member]

Network Service and Systems Integration Business [Member]

Network Service and Systems Integration Business [Member]

ATM Operation Business [Member]

ATM Operation Business [Member]

ATM Operation Business [Member]

ATM Operation Business [Member]

ATM Operation Business [Member]

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

Goodwill [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Goodwill, gross

¥ 6,090,233

$59,140

¥ 6,090,233

$59,140

¥ 5,908,615

¥ 5,854,682

$56,853

¥ 5,854,682

$56,853

¥ 5,673,064

$2,287

¥ 235,551

$2,287

¥ 235,551

¥ 235,551

Accumulated impairment losses

-120,282

-1,168

-120,282

-1,168

-120,282

-120,282

-1,168

-120,282

-1,168

-120,282

'

'

'

'

'

Goodwill, net

5,969,951

57,972

5,969,951

57,972

5,788,333

5,734,400

55,685

5,734,400

55,685

5,552,782

2,287

235,551

2,287

235,551

235,551

Acquisition

¥ 181,618

'

'

'

'

¥ 181,618

'

'

'

'

'

'

'

'

'

Note_9_Leases_Details

Note 9 - Leases (Details)

12 Months Ended

In Thousands, unless otherwise specified

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

Backbone Line [Member]

Backbone Line [Member]

Backbone Line [Member]

Backbone Line [Member]

Local Access Lines [Member]

Local Access Lines [Member]

Local Access Lines [Member]

Local Access Lines [Member]

Other Lease and Rental [Member]

Other Lease and Rental [Member]

Other Lease and Rental [Member]

Other Lease and Rental [Member]

Due February 2018 [Member]

Due February 2019 [Member]

Due February 2019 [Member]

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

Note 9 - Leases (Details) [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Deposits Assets, Current

$14,199

¥ 1,462,223

¥ 1,200

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Operating Leases, Rent Expense

'

'

'

'

36,549

3,763,803

3,535,213

3,370,813

219,483

22,602,364

22,464,593

23,101,650

63,247

6,513,184

5,978,985

5,949,230

'

'

'

Operating Leases, Income Statement, Sublease Revenue

234

24,082

29,160

2,394

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Proceeds from Sale of Machinery and Equipment

5,190

534,479

593,715

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Minimum Lease Payments, Sale Leaseback Transactions

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

637,548

5,687

585,610

Capital Leased Assets, Noncurrent, Fair Value Disclosure

222,070

22,868,800

21,864,989

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Capital Leases, Lessee Balance Sheet, Assets by Major Class, Property, Plant, and Equipment Other, Accumulated Depreciation

143,678

14,795,972

13,340,942

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Capital Leases, Net Investment in Sales Type Leases, Executory Costs

$2,608

¥ 268,598

¥ 301,643

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Note_9_Leases_Details_Refundab

Note 9 - Leases (Details) - Refundable Guarantee Deposits

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

In Thousands, unless otherwise specified

USD ($)

JPY (¥)

JPY (¥)

Head Office [Member]

Head Office [Member]

Head Office [Member]

Sales and Subsidiaries Offices [Member]

Sales and Subsidiaries Offices [Member]

Sales and Subsidiaries Offices [Member]

Others [Member]

Others [Member]

Others [Member]

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

Note 9 - Leases (Details) - Refundable Guarantee Deposits [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

Refundable guarantee deposits

$12,280

¥ 1,264,535

¥ 2,051,449

$6,472

[1]

¥ 666,480

[1]

¥ 1,472,311

[1]

$5,386

¥ 554,610

¥ 543,181

$422

¥ 43,445

¥ 35,957

[1]

Guarantee deposits-current related to the present head office in amount of 1,462,223 thousand ($14,199 thousand) was excluded from the tableabove. The Company will relocate the head office on June 2014.

Note_9_Leases_Details_Lessee_F

Note 9 - Leases (Details) - Lessee Future Minimum Lease Payments	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014
In Thousands, unless otherwise specified	USD ($)	JPY (¥)	JPY (¥)	Connectivity Lines [Member]	Connectivity Lines [Member]	Other Operating Leases [Member]	Other Operating Leases [Member]
				USD ($)	JPY (¥)	USD ($)	JPY (¥)
Note 9 - Leases (Details) - Lessee Future Minimum Lease Payments [Line Items]	'	'	'	'	'	'	'
2015	'	'	'	$19	¥ 1,914	$20,393	¥ 2,100,021
2015	37,828	3,895,597	'	'	'	'	'
2016	'	'	'	'	'	27,119	2,792,711
2016	26,425	2,721,272	'	'	'	'	'
2017	'	'	'	'	'	27,155	2,796,420
2017	14,009	1,442,649	'	'	'	'	'
2018	'	'	'	'	'	5,291	544,892
2018	4,333	446,161	'	'	'	'	'
2019	'	'	'	'	'	466	47,999
2019	1,106	113,880	'	'	'	'	'
2020 and thereafter	'	'	'	'	'	806	83,002
Total minimum lease payments	'	'	'	19	1,914	81,230	8,365,045
Total minimum lease payments	83,701	8,619,559	'	'	'	'	'
Less amounts representing interest	2,556	263,211	'	'	'	'	'
Present value of net minimum capital lease payments	81,145	8,356,348	'	'	'	'	'
Less current portion	36,444	3,753,026	3,505,471	'	'	'	'
Noncurrent portion	$44,701	¥ 4,603,322	¥ 5,370,365	'	'	'	'

Note_9_Leases_Details_SalesTyp

Note 9 - Leases (Details) - Sales-Type Leases	Mar. 31, 2014		Mar. 31, 2014		Mar. 31, 2013
In Thousands, unless otherwise specified	USD ($)		JPY (¥)		JPY (¥)
Sales-Type Leases [Abstract]	'		'		'
2015	$6,543		¥ 673,758		'
2016	5,216		537,130		'
2017	1,486		153,049		'
2018	672		69,177		'
2019	16		1,701		'
Total minimum lease payments to be received*	13,933	[1]	1,434,815	[1]	1,405,258	[1]
Less unearned income	217		22,364		30,400
Net investment in sales-type leases	13,716		1,412,451		1,374,858
Less current portion	6,406		659,677		476,818
Non-current net investment in sales-type leases	$7,310		¥ 752,774		¥ 898,040
[1]	Estimated executory costs, including profit thereon, of 301,643 thousand and 268,598 thousand ($2,608 thousand) were excluded from total minimum lease payments to be received as of March 31, 2013 and 2014, respectively.

Note_10_Asset_Retirement_Oblig2

Note 10 - Asset Retirement Obligations (Details) - Asset Retirement Obligations	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013
	USD ($)	JPY (¥)	JPY (¥)
Asset Retirement Obligations [Abstract]	'	'	'
Balance at beginning of the year	$3,249	¥ 334,585	¥ 299,083
Liabilities incurred	1,186	122,157	26,620
Accretion expense	78	8,041	8,882
Revision in estimated cash flows related to head office relocation	473	48,657	'
Balance at end of the year	$4,986	¥ 513,440	¥ 334,585

Note_11_Borrowings_Details

Note 11 - Borrowings (Details)	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013
In Thousands, unless otherwise specified	USD ($)	JPY (¥)
Debt Disclosure [Abstract]	'	'	'
Short-term Debt, Weighted Average Interest Rate	0.60%	0.60%	0.69%
Line of Credit Facility, Maximum Borrowing Capacity	$102,933	¥ 10,600,000	'

Note_11_Borrowings_Details_Lon

Note 11 - Borrowings (Details) - Long-Term Borrowing	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013
In Thousands, unless otherwise specified	USD ($)	JPY (¥)	JPY (¥)
Debt Instrument [Line Items]	'	'	'
Long-term installment payable at various dates through calendar 2014. Interest is payable at variable rates based on Tokyo InterBank Offered Rate (TIBOR) which were 0.250% and 0.212% as of March 31, 2013 and 2014, respectively. Weighted average interest rates were 0.962% and 0.901% at March 31, 2013 and 2014, respectively.	$9,517	¥ 980,000	¥ 1,990,000
Less current portion	-9,517	-980,000	-1,010,000
Long-term borrowings, less current portion	'	'	¥ 980,000

Note_11_Borrowings_Details_Lon1

Note 11 - Borrowings (Details) - Long-Term Borrowing (Parentheticals)	Mar. 31, 2014	Mar. 31, 2013
Debt Instrument [Line Items]	'	'
Weighted average interest rate	0.90%	0.96%
TIBOR [Member]	'	'
Debt Instrument [Line Items]	'	'
TIBOR rate	0.21%	0.25%

Note_11_Borrowings_Details_Ann

Note 11 - Borrowings (Details) - Annual Maturities of Long-Term Borrowings	Mar. 31, 2014	Mar. 31, 2014
In Thousands, unless otherwise specified	USD ($)	JPY (¥)
Annual Maturities of Long-Term Borrowings [Abstract]	'	'
2015	$9,517	¥ 980,000

Note_12_Income_Taxes_Details

Note 12 - Income Taxes (Details)

12 Months Ended

Mar. 31, 2016

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2013

Mar. 31, 2013

Mar. 31, 2013

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

Japan [Member]

Internal Revenue Service (IRS) [Member]

Japan [Member]

Japan [Member]

United States [Member]

United States [Member]

Other Countries [Member]

Other Countries [Member]

USD ($)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

Note 12 - Income Taxes (Details) [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent

35.90%

38.30%

38.30%

38.30%

41.00%

'

'

'

'

'

'

'

'

Decrease in Deferred Tax Liability Net

'

'

'

'

¥ 110,381,000

'

'

'

'

'

'

'

'

Increase in Deferred Tax Liability, Net

'

1,034,000

106,487,000

'

'

'

'

'

'

'

'

'

'

Valuation Allowance, Deferred Tax Asset, Change in Amount

'

-9,066,000

-933,623,000

-647,079,000

-136,689,000

'

'

'

'

'

'

'

'

Undistributed Earnings of Foreign Subsidiaries

'

3,914,000

403,040,000

'

'

'

'

'

'

'

'

'

'

Operating Loss Carryforwards

'

'

'

'

'

'

'

22,434,000

2,310,209,000

9,876,000

1,017,046,000

4,114,000

423,705,000

Unrecognized Tax Benefits

'

'

¥ 0

¥ 0

'

'

'

'

'

'

'

'

'

Open Tax Year

'

'

'

'

'

'2013

'2006

'

'

'

'

'

'

Note_12_Income_Taxes_Details_I

Note 12 - Income Taxes (Details) - Income From Operations Before Income Tax Expense	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
	USD ($)	JPY (¥)	JPY (¥)	JPY (¥)
Income from operations before income tax expense and equity in net income of equity method investees:	'	'	'	'
Domestic	$62,208	¥ 6,406,153	¥ 7,825,846	¥ 5,970,007
Foreign	-1,275	-131,262	-68,982	6,213
Total	60,933	6,274,891	7,756,864	5,976,220
Income taxes―current:	'	'	'	'
Domestic	23,825	2,453,549	3,140,964	2,489,350
Foreign	404	41,582	-6,254	422
Total	24,229	2,495,131	3,134,710	2,489,772
Income taxes―deferred:	'	'	'	'
Domestic	-7,087	-729,822	-528,832	35,714
Foreign	291	29,996	1,704	'
Total	($6,796)	¥ (699,826)	¥ (527,128)	¥ 35,714

Note_12_Income_Taxes_Details_D

Note 12 - Income Taxes (Details) - Deferred Tax Assets and Liabilities

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

In Thousands, unless otherwise specified

USD ($)

JPY (¥)

JPY (¥)

Customer Relationships [Member]

Customer Relationships [Member]

Customer Relationships [Member]

Trademarks [Member]

Trademarks [Member]

Trademarks [Member]

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

Note 12 - Income Taxes (Details) - Deferred Tax Assets and Liabilities [Line Items]

'

'

'

'

'

'

'

'

'

Unrealized gains on available‑for‑sale securities

$8,225

¥ 847,033

¥ 290,623

'

'

'

'

'

'

Capital leases

1,037

106,807

73,735

'

'

'

'

'

'

Accrued expenses

7,272

748,875

713,056

'

'

'

'

'

'

Retirement and pension cost

7,929

816,558

758,240

'

'

'

'

'

'

Allowance for doubtful accounts

475

48,885

66,170

'

'

'

'

'

'

Depreciation

'

'

48,315

'

'

'

'

'

'

Net loss on other investments

2,337

240,698

285,505

'

'

'

'

'

'

Operating loss carryforwards

13,306

1,370,277

1,416,522

'

'

'

'

'

'

Transactions in transit*

'

[1]

'

[1]

'

[1]

'

'

'

'

'

'

Transactions in transit*

845

[1]

86,953

[1]

47,983

[1]

'

'

'

'

'

'

Impairment loss on telephone rights

755

77,690

77,101

'

'

'

'

'

'

Accrued enterprise tax

983

101,252

179,725

'

'

'

'

'

'

Asset retirement obligation

1,790

184,325

120,116

'

'

'

'

'

'

Deferred revenue

5,963

614,054

468,382

'

'

'

'

'

'

Intangible assets

'

'

'

14,616

1,505,159

1,690,781

373

38,413

38,413

Investments in equity method investees

2,268

233,550

168,061

'

'

'

'

'

'

Other

2,109

217,213

237,761

'

'

'

'

'

'

Other

1,615

166,346

159,753

'

'

'

'

'

'

Total

47,033

4,843,452

5,014,984

'

'

'

'

'

'

Total

34,647

3,567,953

2,923,913

'

'

'

'

'

'

Valuation allowance

-4,158

-428,184

-1,361,807

'

'

'

'

'

'

Total

42,875

4,415,268

3,653,177

'

'

'

'

'

'

Total

34,647

3,567,953

2,923,913

'

'

'

'

'

'

Tax deduction of goodwill

6,705

690,499

528,299

'

'

'

'

'

'

Excess of tax deductible goodwill over the reported amount of goodwill

$3,077

¥ 316,818

¥ 570,356

'

'

'

'

'

'

[1]

This item arises from transactions between IIJ and foreign subsidiaries, which were recorded in the different periods as a result of the difference in each company's fiscal year-end.

Note_12_Income_Taxes_Details_O

Note 12 - Income Taxes (Details) - Operating Loss Carryforwards

Mar. 31, 2019

Mar. 31, 2019

Mar. 31, 2018

Mar. 31, 2018

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2019

Mar. 31, 2019

Mar. 31, 2018

Mar. 31, 2018

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2019

Mar. 31, 2019

Mar. 31, 2018

Mar. 31, 2018

Mar. 31, 2014

Mar. 31, 2014

In Thousands, unless otherwise specified

Enterprise Tax [Member]

Enterprise Tax [Member]

Enterprise Tax [Member]

Enterprise Tax [Member]

Enterprise Tax [Member]

Enterprise Tax [Member]

Inhabitant Tax [Member]

Inhabitant Tax [Member]

Inhabitant Tax [Member]

Inhabitant Tax [Member]

Inhabitant Tax [Member]

Inhabitant Tax [Member]

Others [Member]

Others [Member]

Others [Member]

Others [Member]

Others [Member]

Others [Member]

USD ($)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

Note 12 - Income Taxes (Details) - Operating Loss Carryforwards [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Operating Loss Carryforward

$2,153

¥ 221,664

$370

¥ 38,120

$2,523

¥ 259,784

$609

¥ 62,745

$105

¥ 10,762

$714

¥ 73,507

$32,430

¥ 3,339,609

$3,994

¥ 411,351

$36,424

¥ 3,750,960

Note_12_Income_Taxes_Details_I1

Note 12 - Income Taxes (Details) - Income Tax Reconciliation	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
	USD ($)	JPY (¥)	JPY (¥)	JPY (¥)
Income Tax Reconciliation [Abstract]	'	'	'	'
Amount computed by using normal Japanese statutory tax rate	$23,337	¥ 2,403,283	¥ 2,970,879	¥ 2,450,250
Increase (decrease) in taxes resulting from:	'	'	'	'
Expenses not deductible for tax purpose	997	102,634	89,012	81,115
Inhabitant tax―per capita	360	37,122	35,809	34,415
Expiration of operating loss carryforward	'	'	'	176,829
Change in valuation allowance	-9,295	-957,182	-666,973	-107,171
Tax effects on investments in equity method investees	636	65,489	168,061	'
Enterprise tax―not based on income	798	82,191	77,868	68,960
Tax rate change	1,034	106,487	'	-110,381
Other—net	-434	-44,719	-67,074	-68,531
Income tax expense as reported	$17,433	¥ 1,795,305	¥ 2,607,582	¥ 2,525,486

Note_13_Retirement_and_Pension2

Note 13 - Retirement and Pension Plans (Details)

12 Months Ended

12 Months Ended

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Jun. 30, 2011

Jun. 30, 2011

Mar. 31, 2013

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

Debt Securities [Member]

Equity Securities [Member]

Other Financial Instruments [Member]

Contributions Allocated to Life Insurance Pooled Investment Portfolios [Member]

Contributions Allocated to Debt Securities, Equity Securities, and Other Financial Instruments [Member]

Parent Company and Subsidiaries [Member]

Parent Company and Subsidiaries [Member]

Parent Company and Subsidiaries [Member]

Auditor Retirement Benefits [Member]

Auditor Retirement Benefits [Member]

Auditor Retirement Benefits [Member]

Full-Time Director Benefits [Member]

Full-Time Director Benefits [Member]

Minimum [Member]

Full-Time Director Benefits [Member]

Full-Time Director Benefits [Member]

Full-Time Director Benefits [Member]

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

Note 13 - Retirement and Pension Plans (Details) [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Defined Benefit Plan, Accumulated Benefit Obligation

$26,859,000

¥ 2,765,988,000

¥ 2,444,643,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets, Aggregate Accumulated Benefit Obligation

42,985,000

4,426,598,000

3,855,332,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Defined Benefit Plan, Plans with Benefit Obligations in Excess of Plan Assets, Aggregate Fair Value of Plan Assets

23,543,000

2,424,499,000

2,012,611,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Defined Benefit Plan, Plans with Benefit Obligations in Excess of Plan Assets, Aggregate Benefit Obligation

771,000

79,449,000

70,425,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Defined Benefit Plan Unrecognized Net Loss, Amortization Period

'14 years

'14 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Defined Benefit Plan Unrecognized Net Obligation, Amortization Period

'21 years

'21 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Defined Benefit Plan, Future Amortization of Gain (Loss)

'

0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Defined Benefit Plan, Future Amortization of Transition Obligation (Asset)

4,000

369,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Defined Benefit Plans, Estimated Future Employer Contributions in Next Fiscal Year

2,880,000

296,630,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Defined Contribution Plan, Maximum Annual Contributions Per Employee, Percent

1.60%

1.60%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Defined Contribution Plan, Maximum Annual Contributions Per Employee, Amount

'

0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Pension Contributions

1,216,000

125,195,000

114,450,000

109,224,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Defined Benefit Plan, Target Plan Asset Allocations

'

'

'

'

63.00%

35.00%

2.00%

50.00%

50.00%

'

'

'

'

'

'

'

'

'

Multiemployer Plan, Period Contributions

2,578,000

265,470,000

244,666,000

214,987,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Multiemployer Plan Period Contributions, Percentage

5.00%

5.00%

5.00%

5.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Multiemployer Plans, Funded Status, Percentage

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

80.00%

Multiemployer Plans, Plan Assets

6,088,452,000

626,988,803,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Other Postretirement Benefits Payable

'

'

'

'

'

'

'

'

'

2,611,000

268,921,000

265,674,000

34,000

3,520,000

3,690,000

2,479,000

255,330,000

'

Other Postretirement Benefits Payments

$20,000

¥ 2,010,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Note_13_Retirement_and_Pension3

Note 13 - Retirement and Pension Plans (Details) - Net Periodic Pension Cost	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
	USD ($)	JPY (¥)	JPY (¥)	JPY (¥)
Net Periodic Pension Cost [Abstract]	'	'	'	'
Service cost	$5,269	¥ 542,584	¥ 479,158	¥ 467,583
Interest cost	441	45,418	46,975	48,335
Expected return on plan assets	-470	-48,303	-29,796	-27,086
Amortization of transition obligation	4	369	369	369
Other	'	'	'	-12,632
Net periodic pension cost	$5,244	¥ 540,068	¥ 496,706	¥ 476,569

Note_13_Retirement_and_Pension4

Note 13 - Retirement and Pension Plans (Details) - Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
	USD ($)	JPY (¥)	JPY (¥)	JPY (¥)
Other Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income [Abstract]	'	'	'	'
Net actuarial loss (gain)	($619)	¥ (63,775)	¥ 92,808	¥ 39,083
Amortization of transition obligation in net periodic pension cost	-4	-369	-369	-369
Other	'	'	'	12,632
Amounts recognized in other comprehensive income (loss)	-623	-64,144	92,439	51,346
Total net periodic pension cost and amounts recognized in other comprehensive income	$4,621	¥ 475,924	¥ 589,145	¥ 527,915

Note_13_Retirement_and_Pension5

Note 13 - Retirement and Pension Plans (Details) - Change in Benefit Obligation and Plan Assets	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
	USD ($)	JPY (¥)	JPY (¥)	JPY (¥)
Change in benefit obligation:	'	'	'	'
Benefit obligation at beginning of year	$37,438	¥ 3,855,332	¥ 3,196,857	'
Service cost	5,269	542,584	479,158	467,583
Interest cost	441	45,418	46,975	48,335
Actuarial loss	166	17,098	209,406	'
Benefit paid	-329	-33,834	-77,064	'
Benefit obligation at end of year	42,985	4,426,598	3,855,332	3,196,857
Fair value of plan assets at beginning of year	19,544	2,012,611	1,655,373	'
Actual return on plan assets	1,254	129,176	146,394	'
Employer contribution	2,880	296,631	257,288	'
Benefits paid	-135	-13,919	-46,444	'
Fair value of plan assets at end of year	23,543	2,424,499	2,012,611	1,655,373
Funded status at end of year	($19,442)	¥ (2,002,099)	¥ (1,842,721)	'

Note_13_Retirement_and_Pension6

Note 13 - Retirement and Pension Plans (Details) - Amounts Recognized in Consolidated Balance Sheets	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013
In Thousands, unless otherwise specified	USD ($)	JPY (¥)	JPY (¥)
Amounts Recognized in Consolidated Balance Sheets [Abstract]	'	'	'
Accrued retirement and pension costs―noncurrent	($19,442)	¥ (2,002,099)	¥ (1,842,721)

Note_13_Retirement_and_Pension7

Note 13 - Retirement and Pension Plans (Details) - Amounts Recognized in Accumulated Other Comprehensive Income	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013
In Thousands, unless otherwise specified	USD ($)	JPY (¥)	JPY (¥)
Amounts Recognized in Accumulated Other Comprehensive Income [Abstract]	'	'	'
Net actuarial loss	$2,343	¥ 241,275	¥ 305,049
Obligation at transition	7	734	1,104
Total	$2,350	¥ 242,009	¥ 306,153

Note_13_Retirement_and_Pension8

Note 13 - Retirement and Pension Plans (Details) - Actuarial Assumptions	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Actuarial Assumptions [Abstract]	'	'	'
Discount rate	1.70%	1.20%	'
Discount rate	1.20%	1.50%	1.80%
Expected long-term rate of return on plan assets	2.40%	1.80%	1.90%
Rate of increase in compensation	3.20%	3.30%	'
Rate of increase in compensation	3.30%	3.30%	3.40%

Note_13_Retirement_and_Pension9

Note 13 - Retirement and Pension Plans (Details) - Benefit Payments Expected to Be Paid	Mar. 31, 2014	Mar. 31, 2014
In Thousands, unless otherwise specified	USD ($)	JPY (¥)
Benefit Payments Expected to Be Paid [Abstract]	'	'
2015	$622	¥ 64,015
2016	734	75,530
2017	964	99,316
2018	1,202	123,816
2019	1,306	134,463
2020－2024	12,420	1,279,018
Total	$17,248	¥ 1,776,158

Recovered_Sheet1

Note 13 - Retirement and Pension Plans (Details) - Basis of Fair Value Measurement of Pension Plan Assets in Yen

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

In Thousands, unless otherwise specified

USD ($)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Other Financial Instruments [Member]

Other Financial Instruments [Member]

Other Financial Instruments [Member]

Other Financial Instruments [Member]

Other Financial Instruments [Member]

Other Financial Instruments [Member]

Cash [Member]

Cash [Member]

Cash [Member]

Cash [Member]

Cash [Member]

Cash [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

Japanese Equity Securities [Member]

Japanese Equity Securities [Member]

Japanese Equity Securities [Member]

Japanese Equity Securities [Member]

Japanese Equity Securities [Member]

Japanese Equity Securities [Member]

U.S. Equity Securities [Member]

U.S. Equity Securities [Member]

U.S. Equity Securities [Member]

U.S. Equity Securities [Member]

U.S. Equity Securities [Member]

U.S. Equity Securities [Member]

Other Equity Securities - Developed Countries [Member]

Other Equity Securities - Developed Countries [Member]

Other Equity Securities - Developed Countries [Member]

Other Equity Securities - Developed Countries [Member]

Other Equity Securities - Developed Countries [Member]

Other Equity Securities - Developed Countries [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

JPY (¥)

JPY (¥)

Japanese Government and Municipalities [Member]

Japanese Government and Municipalities [Member]

Japanese Government and Municipalities [Member]

Japanese Government and Municipalities [Member]

Japanese Government and Municipalities [Member]

Japanese Government and Municipalities [Member]

Domestic Corporate Debt Securities [Member]

Domestic Corporate Debt Securities [Member]

Domestic Corporate Debt Securities [Member]

Domestic Corporate Debt Securities [Member]

Domestic Corporate Debt Securities [Member]

Domestic Corporate Debt Securities [Member]

US Government Agencies Debt Securities [Member]

US Government Agencies Debt Securities [Member]

US Government Agencies Debt Securities [Member]

US Government Agencies Debt Securities [Member]

US Government Agencies Debt Securities [Member]

US Government Agencies Debt Securities [Member]

Other Government Debt Securities - Developed Countries [Member]

Other Government Debt Securities - Developed Countries [Member]

Other Government Debt Securities - Developed Countries [Member]

Other Government Debt Securities - Developed Countries [Member]

Other Government Debt Securities - Developed Countries [Member]

Other Government Debt Securities - Developed Countries [Member]

Residential Mortgage Backed Securities [Member]

Residential Mortgage Backed Securities [Member]

Residential Mortgage Backed Securities [Member]

Residential Mortgage Backed Securities [Member]

Residential Mortgage Backed Securities [Member]

Residential Mortgage Backed Securities [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

JPY (¥)

JPY (¥)

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

USD ($)

JPY (¥)

JPY (¥)

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

USD ($)

JPY (¥)

JPY (¥)

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

USD ($)

JPY (¥)

JPY (¥)

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

JPY (¥)

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

USD ($)

JPY (¥)

JPY (¥)

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

USD ($)

JPY (¥)

JPY (¥)

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

USD ($)

JPY (¥)

JPY (¥)

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

USD ($)

JPY (¥)

JPY (¥)

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

Note 13 - Retirement and Pension Plans (Details) - Basis of Fair Value Measurement of Pension Plan Assets in Yen [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Pension Plan Assets at Fair Value

$23,543

¥ 2,424,499

$19,544

¥ 2,012,611

¥ 1,655,373

$3,387

¥ 348,758

¥ 302,533

$3,387

¥ 348,758

¥ 302,533

$867

¥ 89,304

¥ 72,760

$867

¥ 89,304

¥ 72,760

$597

¥ 61,498

¥ 51,220

$597

¥ 61,498

¥ 51,220

¥ 499,560

¥ 426,513

¥ 499,560

¥ 426,513

$4,722

¥ 486,308

¥ 477,430

$4,722

¥ 486,308

¥ 477,430

$1,593

¥ 164,037

¥ 59,533

$1,593

¥ 164,037

¥ 59,533

$635

¥ 65,339

¥ 74,294

$635

¥ 65,339

¥ 74,294

$1,474

¥ 151,824

¥ 103,471

$1,474

¥ 151,824

¥ 103,471

$188

¥ 19,337

¥ 26,252

$188

¥ 19,337

¥ 26,252

¥ 886,845

¥ 740,980

¥ 886,845

¥ 740,980

$9,225

[1]

¥ 950,011

[1]

¥ 800,968

[1]

$9,225

[1]

¥ 950,011

[1]

¥ 800,968

[1]

$855

¥ 88,083

¥ 44,150

$855

¥ 88,083

¥ 44,150

$5,706

¥ 587,643

¥ 470,663

$17,837

¥ 1,836,856

¥ 1,541,948

[1]

Other financial instruments are life insurance pooled investment portfolios.

Recovered_Sheet2

Note 13 - Retirement and Pension Plans (Details) - Basis of Fair Value Measurement of Pension Plan Assets in US Dollars

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

In Thousands, unless otherwise specified

USD ($)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Equity Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Debt Securities [Member]

Other Financial Instruments [Member]

Other Financial Instruments [Member]

Other Financial Instruments [Member]

Other Financial Instruments [Member]

Other Financial Instruments [Member]

Other Financial Instruments [Member]

Cash [Member]

Cash [Member]

Cash [Member]

Cash [Member]

Cash [Member]

Cash [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

Japanese Equity Securities [Member]

Japanese Equity Securities [Member]

Japanese Equity Securities [Member]

Japanese Equity Securities [Member]

Japanese Equity Securities [Member]

Japanese Equity Securities [Member]

U.S. Equity Securities [Member]

U.S. Equity Securities [Member]

U.S. Equity Securities [Member]

U.S. Equity Securities [Member]

U.S. Equity Securities [Member]

U.S. Equity Securities [Member]

Other Equity Securities - Developed Countries [Member]

Other Equity Securities - Developed Countries [Member]

Other Equity Securities - Developed Countries [Member]

Other Equity Securities - Developed Countries [Member]

Other Equity Securities - Developed Countries [Member]

Other Equity Securities - Developed Countries [Member]

Fair Value, Inputs, Level 1 [Member]

USD ($)

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

JPY (¥)

JPY (¥)

Japanese Government and Municipalities [Member]

Japanese Government and Municipalities [Member]

Japanese Government and Municipalities [Member]

Japanese Government and Municipalities [Member]

Japanese Government and Municipalities [Member]

Japanese Government and Municipalities [Member]

Domestic Corporate Debt Securities [Member]

Domestic Corporate Debt Securities [Member]

Domestic Corporate Debt Securities [Member]

Domestic Corporate Debt Securities [Member]

Domestic Corporate Debt Securities [Member]

Domestic Corporate Debt Securities [Member]

US Government Agencies Debt Securities [Member]

US Government Agencies Debt Securities [Member]

US Government Agencies Debt Securities [Member]

US Government Agencies Debt Securities [Member]

US Government Agencies Debt Securities [Member]

US Government Agencies Debt Securities [Member]

Other Government Debt Securities - Developed Countries [Member]

Other Government Debt Securities - Developed Countries [Member]

Other Government Debt Securities - Developed Countries [Member]

Other Government Debt Securities - Developed Countries [Member]

Other Government Debt Securities - Developed Countries [Member]

Other Government Debt Securities - Developed Countries [Member]

Residential Mortgage Backed Securities [Member]

Residential Mortgage Backed Securities [Member]

Residential Mortgage Backed Securities [Member]

Residential Mortgage Backed Securities [Member]

Residential Mortgage Backed Securities [Member]

Residential Mortgage Backed Securities [Member]

Fair Value, Inputs, Level 2 [Member]

USD ($)

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

JPY (¥)

JPY (¥)

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

USD ($)

JPY (¥)

JPY (¥)

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

USD ($)

JPY (¥)

JPY (¥)

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

USD ($)

JPY (¥)

JPY (¥)

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

Fair Value, Inputs, Level 1 [Member]

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

USD ($)

JPY (¥)

JPY (¥)

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

USD ($)

JPY (¥)

JPY (¥)

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

USD ($)

JPY (¥)

JPY (¥)

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

USD ($)

JPY (¥)

JPY (¥)

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

Note 13 - Retirement and Pension Plans (Details) - Basis of Fair Value Measurement of Pension Plan Assets in US Dollars [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Plan Assets

$23,543

¥ 2,424,499

$19,544

¥ 2,012,611

¥ 1,655,373

$3,387

¥ 348,758

¥ 302,533

$3,387

¥ 348,758

¥ 302,533

$867

¥ 89,304

¥ 72,760

$867

¥ 89,304

¥ 72,760

$597

¥ 61,498

¥ 51,220

$597

¥ 61,498

¥ 51,220

$4,851

$4,851

¥ 499,560

¥ 426,513

¥ 499,560

¥ 426,513

$4,722

¥ 486,308

¥ 477,430

$4,722

¥ 486,308

¥ 477,430

$1,593

¥ 164,037

¥ 59,533

$1,593

¥ 164,037

¥ 59,533

$635

¥ 65,339

¥ 74,294

$635

¥ 65,339

¥ 74,294

$1,474

¥ 151,824

¥ 103,471

$1,474

¥ 151,824

¥ 103,471

$188

¥ 19,337

¥ 26,252

$188

¥ 19,337

¥ 26,252

$8,612

$8,612

¥ 886,845

¥ 740,980

¥ 886,845

¥ 740,980

$9,225

[1]

¥ 950,011

[1]

¥ 800,968

[1]

$9,225

[1]

¥ 950,011

[1]

¥ 800,968

[1]

$855

¥ 88,083

¥ 44,150

$855

¥ 88,083

¥ 44,150

$5,706

¥ 587,643

¥ 470,663

$17,837

¥ 1,836,856

¥ 1,541,948

[1]

Other financial instruments are life insurance pooled investment portfolios.

Note_14_Shareholders_Equity_De

Note 14 - Shareholders' Equity (Details)

0 Months Ended

1 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

0 Months Ended

3 Months Ended

12 Months Ended

Nov. 08, 2013

Nov. 08, 2013

Nov. 08, 2012

Oct. 01, 2012

Nov. 08, 2011

Aug. 31, 2013

Aug. 31, 2013

Jul. 31, 2013

Jul. 31, 2013

Jun. 26, 2013

Jun. 26, 2013

Jun. 27, 2012

Jun. 28, 2011

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Jun. 28, 2006

Oct. 31, 2012

Jan. 01, 2014

Mar. 31, 2012

Mar. 31, 2012

Jul. 11, 2013

Jul. 13, 2012

Jul. 13, 2012

Jul. 14, 2011

Mar. 31, 2014

Mar. 31, 2013

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

JPY (¥)

Options After Stock Split [Member]

Treasury Stock [Member]

GDX [Member]

Trust Networks [Member]

Directors and Executive Officers [Member]

Directors and Executive Officers [Member]

Directors and Executive Officers [Member]

Directors and Executive Officers [Member]

Directors and Executive Officers [Member]

Directors and Executive Officers [Member]

IIJ-Exlayer [Member]

JPY (¥)

JPY (¥)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

Note 14 - Shareholders' Equity (Details) [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Net Assets Minimum Requirement After Dividends

'

'

'

'

'

'

'

'

'

'

'

'

'

'

¥ 3,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Adjustments to Additional Paid in Capital to Eliminate Accumulated Deficit

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

21,980,395,000

'

'

'

'

'

'

'

'

'

'

Adjustments Common Stock to Eliminate Accumulated Deficit

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2,539,222,000

'

'

'

'

'

'

'

'

'

'

Percentage of Dividends Appropriated as Legal Reserve

'

'

'

'

'

'

'

'

'

'

'

'

'

10.00%

10.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

Additional Paid in Capital Percentage of Common Stock

'

'

'

'

'

'

'

'

'

'

'

'

'

25.00%

25.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

Retained Earnings Available For Dividends Under The Company Act

'

'

'

'

'

'

'

'

'

'

'

'

'

204,669,000

21,076,781,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Common Stock, Dividends, Per Share, Declared (in Yen per share)

'

¥ 11

¥ 8.75

'

¥ 7.5

'

'

'

'

'

¥ 10

¥ 8.75

¥ 7.5

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Dividends

4,908,000

505,329,000

354,697,000

'

304,026,000

'

'

'

'

3,936,000

405,368,000

354,697,000

304,026,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Stockholders' Equity Note, Stock Split, Conversion Ratio

'

'

'

200

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Stock Issued During Period, Shares, New Issues (in Shares)

'

'

'

'

'

700,000

700,000

4,700,000

4,700,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Sale of Stock, Price Per Share

'

'

'

'

'

$31.15

¥ 3,208

$32.49

¥ 3,346

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Share Price

'

'

'

'

'

'

'

$31.15

¥ 3,208

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs

'

'

'

'

'

505,000

51,996,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Proceeds from Issuance of Common Stock

'

'

'

'

'

167,714,000

17,271,204,000

'

'

'

'

'

'

167,714,000

17,271,204,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price (in Yen per share)

'

'

'

'

'

'

'

'

'

'

'

'

¥ 1

'

¥ 1

¥ 1

¥ 1

'

'

'

'

'

'

'

'

'

'

'

Options Exercisable Service Period

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'1 year

Options Exercisable Expiration Period

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'29 years

'

Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in Shares)

'

'

'

'

'

'

'

'

'

'

'

'

'

89

89

130

'

'

'

'

'

'

89

130

'

138

'

'

Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

¥ 647,000

¥ 318,562

$6,283

¥ 259,344

'

'

Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in Shares)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

200

'

'

'

'

'

'

'

'

'

Share-based Compensation

'

'

'

'

'

'

'

'

'

'

'

'

'

520,000

53,542,000

40,007,000

26,843,000

'

'

'

'

'

'

'

'

'

'

'

Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized

'

'

'

'

'

'

'

'

'

'

'

'

'

140,000

14,396,000

'

'

'

'

'

'

'

'

'

'

'

'

'

Payments to Noncontrolling Interests

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

5,000

'

'

'

'

'

'

'

Noncontrolling Interest, Increase from Subsidiary Equity Issuance

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

¥ 300,000,000

'

'

'

'

'

'

Treasury Stock Alloted During Period, Shares, Acquisitions (in Shares)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

104

'

'

'

'

'

'

'

'

Note_14_Shareholders_Equity_De1

Note 14 - Shareholders' Equity (Details) - Black-Scholes Option-Pricing Model Assumptions	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Assumptions:	'	'	'
Risk-free interest rate	1.31%	1.30%	1.61%
Expected lives (years)	'15 years	'15 years	'15 years
Expected volatility	55.86%	57.02%	59.89%
Expected dividends	0.54%	0.89%	0.92%

Note_14_Shareholders_Equity_De2

Note 14 - Shareholders' Equity (Details) - Stock Acquisition Rights Plan	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2014	Jun. 28, 2011
	JPY (¥)	JPY (¥)	JPY (¥)	USD ($)	JPY (¥)
Stock Acquisition Rights Plan [Abstract]	'	'	'	'	'
Unexercised options outstanding	'	268	138	346	'
Unexercised options outstanding shares	69,200	53,600	27,600	'	'
Unexercised options outstanding exercise price (in Yen per share)	¥ 1	¥ 1	¥ 1	'	¥ 1
Exercisable options—March 31, 2014	'	'	'	257	'
Exercisable options—March 31, 2014	51,400	'	'	'	'
Exercisable options—March 31, 2014 (in Yen per share)	¥ 1	'	'	'	'
Exercisable options—March 31, 2014	'27 years 288 days	'	'	'	'
Exercisable options—March 31, 2014 (in Yen)	¥ 127,523	'	'	$1,238	'
Exercisable options—March 31, 2014 (in Dollars)	127,523	'	'	1,238	'
Expected to vest after July 10, 2014	'	'	'	89	'
Expected to vest after July 10, 2014	17,800	'	'	'	'
Expected to vest after July 10, 2014 (in Yen per share)	¥ 1	'	'	'	'
Expected to vest after July 10, 2014	'29 years 102 days	'	'	'	'
Expected to vest after July 10, 2014 (in Yen)	44,162	'	'	429	'
Expected to vest after July 10, 2014 (in Dollars)	¥ 44,162	'	'	$429	'
Number of options granted	89	130	'	'	'
Number of shares granted	17,800	26,000	'	'	'
Options granted exercise price (in Yen per share)	¥ 1	¥ 1	'	'	'
Number of Options exercised	11	'	'	'	'
Number of shares exercised	2,200	'	'	'	'
Exercise price options exercised (in Yen per share)	¥ 1	'	'	'	'

Note_14_Shareholders_Equity_De3

Note 14 - Shareholders' Equity (Details) - Effects of Changes in IIJ’s Ownership Interest in Its Subsidiaries in the Company’s Shareholder’s Equity	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2012	Mar. 31, 2014	Mar. 31, 2014
	USD ($)	JPY (¥)	JPY (¥)	JPY (¥)	GDX [Member]	IIJ-Exlayer [Member]	IIJ-Exlayer [Member]
					JPY (¥)	USD ($)	JPY (¥)
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]	'	'	'	'	'	'	'
Net income attributable to IIJ	$43,137	¥ 4,442,237	¥ 5,300,654	¥ 3,640,963	'	'	'
Transfers (to) from the noncontrolling interests	'	'	'	'	'	'	'
Transfers (to) from noncontrolling interest	1	99	'	-85,437	-85,437	1	99
Change from net income attributable to IIJ and transfers (to) from noncontrolling interests	$43,138	¥ 4,442,336	¥ 5,300,654	¥ 3,555,526	'	'	'

Note_15_Other_Comprehensive_In2

Note 15 - Other Comprehensive Income (Loss) (Details) - Tax Effects Allocated to Each Component of Other Comprehensive Income (Loss)	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
	USD ($)	JPY (¥)	JPY (¥)	JPY (¥)
Tax Effects Allocated to Each Component of Other Comprehensive Income (Loss) [Abstract]	'	'	'	'
Foreign currency translation adjustments, before tax amount	$4,074	¥ 419,557	¥ 90,014	¥ (9,539)
Foreign currency translation adjustments, net of tax amount	4,074	419,557	90,014	-9,539
Unrealized holding gain (loss) on securities:	'	'	'	'
Amount arising during the period, before tax amount	16,088	1,656,759	380,637	56,384
Amount arising during the period, tax (expense) benefit	-5,776	-594,776	-136,649	-20,242
Amount arising during the period, net of tax amount	10,312	1,061,983	243,988	36,142
Less: Reclassification adjustments for losses included in net income, before tax amount	-1,045	-107,655	19,788	91,064
Less: Reclassification adjustments for losses included in net income, tax (expense) benefit	400	41,232	-7,579	-37,336
Less: Reclassification adjustments for losses included in net income, net of tax amount	-645	-66,423	12,209	53,728
Other, tax (expense) benefit	-71	-7,421	324	12,875
Other, net of tax amount	-71	-7,421	324	12,875
Net unrealized holding gain (loss) during the period, before tax amount	15,043	1,549,104	400,425	147,448
Net unrealized holding gain (loss) during the period, tax (expense) benefit	-5,447	-560,965	-143,904	-44,703
Net unrealized holding gain (loss) during the period, net of tax amount	9,596	988,139	256,521	102,745
Defined benefit pension plans:	'	'	'	'
Amount arising during the period, before tax amount	619	63,775	-92,808	-39,083
Amount arising during the period, tax (expense) benefit	-222	-22,896	33,319	14,030
Amount arising during the period, net of tax amount	397	40,879	-59,489	-25,053
Less: Reclassification adjustments for gains included in net income, before tax amount	4	369	369	-12,263
Less: Reclassification adjustments for gains included in net income, tax (expense) benefit	-2	-133	-132	5,711
Less: Reclassification adjustments for gains included in net income, net of tax amount	2	236	237	-6,552
Net defined benefit pension plans, before tax amount	623	64,144	-92,439	-51,346
Net defined benefit pension plans, tax (expense) benefit	-224	-23,029	33,187	19,741
Net defined benefit pension plans, net of tax amount	399	41,115	-59,252	-31,605
Other comprehensive income (loss), before tax amount	19,740	2,032,805	398,000	86,563
Other comprehensive income (loss), tax (expense) benefit	-5,671	-583,994	-110,717	-24,962
Other comprehensive income, net of tax	$14,069	¥ 1,448,811	¥ 287,283	¥ 61,601

Note_15_Other_Comprehensive_In3

Note 15 - Other Comprehensive Income (Loss) (Details) - Tax Effects Allocated to Each Component of Other Comprehensive Income (Loss)	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
	USD ($)	JPY (¥)	JPY (¥)	JPY (¥)
Tax Effects Allocated to Each Component of Other Comprehensive Income (Loss) [Abstract]0	'	'	'	'
Foreign currency translation adjustments	$4,074	¥ 419,557	¥ 90,014	¥ (9,539)
Foreign currency translation adjustments	4,074	419,557	90,014	-9,539
Unrealized holding gain (loss) on securities:	'	'	'	'
Amount arising during the period	16,088	1,656,759	380,637	56,384
Amount arising during the period	-5,776	-594,776	-136,649	-20,242
Amount arising during the period	10,312	1,061,983	243,988	36,142
Less: Reclassification adjustments for gains included in net income	-1,045	-107,655	19,788	91,064
Less: Reclassification adjustments for gains included in net income	400	41,232	-7,579	-37,336
Less: Reclassification adjustments for gains included in net income	-645	-66,423	12,209	53,728
Other	-71	-7,421	324	12,875
Other	-71	-7,421	324	12,875
Net unrealized holding gain (loss) during the period	15,043	1,549,104	400,425	147,448
Net unrealized holding gain (loss) during the period	-5,447	-560,965	-143,904	-44,703
Net unrealized holding gain (loss) during the period	9,596	988,139	256,521	102,745
Defined benefit pension plans:	'	'	'	'
Amount arising during the period	619	63,775	-92,808	-39,083
Amount arising during the period	-222	-22,896	33,319	14,030
Amount arising during the period	397	40,879	-59,489	-25,053
Less: Reclassification adjustments for gains included in net income	4	369	369	-12,263
Less: Reclassification adjustments for gains included in net income	-2	-133	-132	5,711
Less: Reclassification adjustments for gains included in net income	2	236	237	-6,552
Net defined benefit pension plans	623	64,144	-92,439	-51,346
Net defined benefit pension plans	-224	-23,029	33,187	19,741
Net defined benefit pension plans	399	41,115	-59,252	-31,605
Other comprehensive income (loss)	19,740	2,032,805	398,000	86,563
Other comprehensive income (loss)	-5,671	-583,994	-110,717	-24,962
Other comprehensive income (loss)	$14,069	¥ 1,448,811	¥ 287,283	¥ 61,601

Note_15_Other_Comprehensive_In4

Note 15 - Other Comprehensive Income (Loss) (Details) - Changes in Accumulated Other Comprehensive Income (Loss) by Component

12 Months Ended

In Thousands, unless otherwise specified

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

Accumulated Net Unrealized Investment Gain (Loss) [Member]

Accumulated Net Unrealized Investment Gain (Loss) [Member]

Accumulated Defined Benefit Plans Adjustment [Member]

Accumulated Defined Benefit Plans Adjustment [Member]

Accumulated Translation Adjustment [Member]

Accumulated Translation Adjustment [Member]

Accumulated Other Comprehensive Income (Loss) [Member]

Accumulated Other Comprehensive Income (Loss) [Member]

Accumulated Other Comprehensive Income (Loss) [Member]

Accumulated Other Comprehensive Income (Loss) [Member]

USD ($)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

Accumulated Other Comprehensive Income (Loss) [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Year Ended

'

¥ 263,770

'

'

$4,809

¥ 495,217

($1,820)

¥ (187,318)

($428)

¥ (44,129)

$2,561

¥ 263,770

'

'

Other comprehensive income before reclassifications

'

'

'

'

10,241

1,054,562

397

40,879

4,075

419,701

14,713

1,515,142

'

'

Amounts reclassified out of accumulated other comprehensive income

'

'

'

'

-645

-66,423

2

236

'

'

-643

-66,187

'

'

Other comprehensive income

14,069

1,448,811

287,283

61,601

9,596

988,139

399

41,115

4,075

419,701

14,070

1,448,955

287,303

61,601

Other

'

'

'

'

'

'

'

'

1

61

1

61

'

'

Year Ended

$16,632

¥ 1,712,786

¥ 263,770

'

$14,405

¥ 1,483,356

($1,421)

¥ (146,203)

$3,648

¥ 375,633

$16,632

¥ 1,712,786

¥ 263,770

'

Note_15_Other_Comprehensive_In5

Note 15 - Other Comprehensive Income (Loss) (Details) - Changes in Accumulated Other Comprehensive Income (Loss) by Component

12 Months Ended

In Thousands, unless otherwise specified

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

Accumulated Net Unrealized Investment Gain (Loss) [Member]

Accumulated Net Unrealized Investment Gain (Loss) [Member]

Accumulated Defined Benefit Plans Adjustment [Member]

Accumulated Defined Benefit Plans Adjustment [Member]

Accumulated Translation Adjustment [Member]

Accumulated Translation Adjustment [Member]

Accumulated Other Comprehensive Income (Loss) [Member]

Accumulated Other Comprehensive Income (Loss) [Member]

Accumulated Other Comprehensive Income (Loss) [Member]

Accumulated Other Comprehensive Income (Loss) [Member]

USD ($)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

Accumulated Other Comprehensive Income (Loss) [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Year Ended

'

¥ 263,770

'

'

$4,809

¥ 495,217

($1,820)

¥ (187,318)

($428)

¥ (44,129)

$2,561

¥ 263,770

'

'

Other comprehensive income before reclassifications

'

'

'

'

10,241

1,054,562

397

40,879

4,075

419,701

14,713

1,515,142

'

'

Amounts reclassified out of accumulated other comprehensive income

'

'

'

'

-645

-66,423

2

236

'

'

-643

-66,187

'

'

Other comprehensive income

14,069

1,448,811

287,283

61,601

9,596

988,139

399

41,115

4,075

419,701

14,070

1,448,955

287,303

61,601

Other

'

'

'

'

'

'

'

'

1

61

1

61

'

'

Year Ended

$16,632

¥ 1,712,786

¥ 263,770

'

$14,405

¥ 1,483,356

($1,421)

¥ (146,203)

$3,648

¥ 375,633

$16,632

¥ 1,712,786

¥ 263,770

'

Note_15_Other_Comprehensive_In6

Note 15 - Other Comprehensive Income (Loss) (Details) - Components of Accumulated Other Comprehensive Income (Loss)	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014
	USD ($)	JPY (¥)	JPY (¥)	JPY (¥)	Accumulated Net Unrealized Investment Gain (Loss) [Member]	Accumulated Net Unrealized Investment Gain (Loss) [Member]	Accumulated Defined Benefit Plans Adjustment [Member]	Accumulated Defined Benefit Plans Adjustment [Member]	Reclassification out of Accumulated Other Comprehensive Income [Member]	Reclassification out of Accumulated Other Comprehensive Income [Member]
					Reclassification out of Accumulated Other Comprehensive Income [Member]	Reclassification out of Accumulated Other Comprehensive Income [Member]	Reclassification out of Accumulated Other Comprehensive Income [Member]	Reclassification out of Accumulated Other Comprehensive Income [Member]	USD ($)	JPY (¥)
					USD ($)	JPY (¥)	USD ($)	JPY (¥)
Note 15 - Other Comprehensive Income (Loss) (Details) - Components of Accumulated Other Comprehensive Income (Loss) [Line Items]	'	'	'	'	'	'	'	'	'	'
Unrealized holding gain on securities	'	'	'	'	$1,045	¥ 107,655	'	'	'	'
Income tax expense	17,433	1,795,305	2,607,582	2,525,486	-400	-41,232	2	133	'	'
Net income	45,481	4,683,632	5,317,347	3,574,510	645	66,423	-2	-236	'	'
Total amount reclassified	43,137	4,442,237	5,300,654	3,640,963	'	'	'	'	643	66,187
Defined benefit pension plans	'	'	'	'	'	'	($4)	¥ (369)	'	'

Note_16_Basic_and_Diluted_Net_2

Note 16 - Basic and Diluted Net Income Per Common Share (Details)	0 Months Ended		6 Months Ended	0 Months Ended	6 Months Ended
	Oct. 01, 2012	Sep. 06, 2012	Oct. 01, 2012	Sep. 06, 2012	Oct. 01, 2012
		Numerator [Member]	Numerator [Member]	Denominator [Member]	Denominator [Member]
Note 16 - Basic and Diluted Net Income Per Common Share (Details) [Line Items]	'	'	'	'	'
Stockholders' Equity Note, Stock Split, Conversion Ratio	200	1	1	200	200

Note_16_Basic_and_Diluted_Net_3

Note 16 - Basic and Diluted Net Income Per Common Share (Details) - Earnings Per Share Calculation Numerator	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
	USD ($)	JPY (¥)	JPY (¥)	JPY (¥)
Numerator―	'	'	'	'
Net income attributable to Internet Initiative Japan Inc.―basic and diluted	$43,137	¥ 4,442,237	¥ 5,300,654	¥ 3,640,963

Note_16_Basic_and_Diluted_Net_4

Note 16 - Basic and Diluted Net Income Per Common Share (Details) - Earnings Per Share Calculation Denominator	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Denominator:	'	'	'
Weighted-average common shares outstanding―basic	44,306,680	40,536,800	40,536,800
Dilutive effect of stock options	54,403	35,800	19,600
Weighted-average common shares outstanding―diluted	44,361,083	40,572,600	40,556,400

Note_16_Basic_and_Diluted_Net_5

Note 16 - Basic and Diluted Net Income Per Common Share (Details) - Earnings Per Share Basic and Diluted	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
	USD ($)	JPY (¥)	JPY (¥)	JPY (¥)
Earnings Per Share Basic and Diluted [Abstract]	'	'	'	'
Basic net income attributable to Internet Initiative Japan Inc. per common share	$0.97	¥ 100.26	¥ 130.76	¥ 89.82
Diluted net income attributable to Internet Initiative Japan Inc. per common share	$0.97	¥ 100.14	¥ 130.65	¥ 89.78

Note_17_Commitments_And_Contin1

Note 17 - Commitments And Contingent Liabilities (Details)	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014
In Millions, unless otherwise specified	Investment Per Fund [Member]	May 2006, January 2007 and January 2008 Agreements [Member]	April 2013 Agreement [Member]
	May 2006, January 2007 and January 2008 Agreements [Member]	USD ($)	JPY (¥)
	USD ($)
Note 17 - Commitments And Contingent Liabilities (Details) [Line Items]	'	'	'
Contractual Obligation	$5	$15	¥ 100
Payments to Acquire Investments	'	$12.60	¥ 19

Note_18_Financial_Instruments_1

Note 18 - Financial Instruments (Details)	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013
In Thousands, unless otherwise specified	Non Marketable Equity Securities [Member]	Non Marketable Equity Securities [Member]	Non Marketable Equity Securities [Member]	Investments In Funds [Member]	Investments In Funds [Member]	Investments In Funds [Member]
	USD ($)	JPY (¥)	JPY (¥)	USD ($)	JPY (¥)	JPY (¥)
Note 18 - Financial Instruments (Details) [Line Items]	'	'	'	'	'	'
Fair Value, Estimate Not Practicable, Investments	$13,397	¥ 1,379,623	¥ 1,121,444	$11,897	¥ 1,225,183	¥ 1,339,895

Note_18_Financial_Instruments_2

Note 18 - Financial Instruments (Details) - Carrying Amounts and Fair Value of Financial Instruments	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013
In Thousands, unless otherwise specified	USD ($)	JPY (¥)	JPY (¥)	Estimate of Fair Value Measurement [Member]	Estimate of Fair Value Measurement [Member]	Estimate of Fair Value Measurement [Member]	Portion at Other than Fair Value Measurement [Member]	Portion at Other than Fair Value Measurement [Member]	Portion at Other than Fair Value Measurement [Member]
				USD ($)	JPY (¥)	JPY (¥)	USD ($)	JPY (¥)	JPY (¥)
Note 18 - Financial Instruments (Details) - Carrying Amounts and Fair Value of Financial Instruments [Line Items]	'	'	'	'	'	'	'	'	'
Practicable to estimate fair value	$61,719	¥ 6,355,817	¥ 3,771,262	$36,425	¥ 3,751,011	¥ 1,309,923	$25,294	¥ 2,604,806	¥ 2,461,339
Practicable to estimate fair value	'	'	'	36,425	3,751,011	1,309,923	'	'	'
Not practicable	61,719	6,355,817	3,771,262	36,425	3,751,011	1,309,923	25,294	2,604,806	2,461,339
Not practicable	'	'	'	'	'	'	'	'	'
Noncurrent refundable insurance policies (other assets)	612	63,062	64,020	'	'	'	'	'	'
Noncurrent refundable insurance policies (other assets)	$612	¥ 63,062	¥ 64,020	'	'	'	'	'	'

Note_19_Fair_Value_Measurement2

Note 19 - Fair Value Measurements (Details)	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2013
	USD ($)	JPY (¥)	JPY (¥)	Hi Ho Trademark [Member]
				JPY (¥)
Note 19 - Fair Value Measurements (Details) [Line Items]	'	'	'	'
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount	'	¥ 0	¥ 0	'
Indefinite-Lived Trademarks	1,039,000	107,000,000	107,000,000	155,000,000
Indefinite-lived Intangible Assets (Excluding Goodwill), Fair Value Disclosure	'	'	'	107,000,000
Impairment of Intangible Assets, Indefinite-lived (Excluding Goodwill)	'	'	'	¥ 48,000,000

Note_19_Fair_Value_Measurement3

Note 19 - Fair Value Measurements (Details) - Assets Measured at Fair Value on a Recurring Basis in Yen	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013
In Thousands, unless otherwise specified	USD ($)	JPY (¥)	JPY (¥)	Fair Value, Inputs, Level 1 [Member]	Fair Value, Inputs, Level 1 [Member]	Fair Value, Inputs, Level 1 [Member]
				USD ($)	JPY (¥)	JPY (¥)
Assets―	'	'	'	'	'	'
Available-for-sale securities―equity securities	$36,425	¥ 3,751,011	¥ 1,309,923	$36,425	¥ 3,751,011	¥ 1,309,923

Note_19_Fair_Value_Measurement4

Note 19 - Fair Value Measurements (Details) - Assets Measured at Fair Value on a Recurring Basis in Us Dollars	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013
In Thousands, unless otherwise specified	USD ($)	JPY (¥)	JPY (¥)	Fair Value, Inputs, Level 1 [Member]	Fair Value, Inputs, Level 1 [Member]	Fair Value, Inputs, Level 1 [Member]
				USD ($)	JPY (¥)	JPY (¥)
Assets―	'	'	'	'	'	'
Available-for-sale securities―equity securities	$36,425	¥ 3,751,011	¥ 1,309,923	$36,425	¥ 3,751,011	¥ 1,309,923

Note_19_Fair_Value_Measurement5

Note 19 - Fair Value Measurements (Details) - Assets Measured at Fair Value on a Nonrecurring Basis in Yen (JPY ¥)	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Assets:	'	'
Trademark	¥ 48,000	¥ 37,000
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]	'	'
Assets:	'	'
Trademark	107,000	'
	107,000	'
Fair Value, Measurements, Nonrecurring [Member]	'	'
Assets:	'	'
Trademark	48,000	'
	¥ 48,000	'

Note_19_Fair_Value_Measurement6

Note 19 - Fair Value Measurements (Details) - Significant Unobservable Inputs (Trademarks [Member], JPY ¥)	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2013
Trademarks [Member]	'
Fair Value Inputs, Assets, Quantitative Information [Line Items]	'
Trademark	¥ 107,000
Trademark	'Relief from royalty method
Trademark	7.50%
Trademark	0.30%

Note_20_Business_Segments_Deta

Note 20 - Business Segments (Details)	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
	USD ($)	JPY (¥)	JPY (¥)	JPY (¥)	IBM Japan [Member]	IBM Japan [Member]	IBM Japan [Member]	IBM Japan [Member]
					USD ($)	JPY (¥)	JPY (¥)	JPY (¥)
Note 20 - Business Segments (Details) [Line Items]	'	'	'	'	'	'	'	'
Revenues	$1,109,655	¥ 114,272,351	¥ 106,248,486	¥ 97,314,605	$127,456	¥ 13,125,454	¥ 13,456,203	¥ 14,396,722

Note_20_Business_Segments_Deta1

Note 20 - Business Segments (Details) - Segment Revenues

12 Months Ended

In Thousands, unless otherwise specified

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

Network Service and Systems Integration Business [Member]

Network Service and Systems Integration Business [Member]

Network Service and Systems Integration Business [Member]

Network Service and Systems Integration Business [Member]

Network Service and Systems Integration Business [Member]

Network Service and Systems Integration Business [Member]

Network Service and Systems Integration Business [Member]

Network Service and Systems Integration Business [Member]

Network Service and Systems Integration Business [Member]

Network Service and Systems Integration Business [Member]

Network Service and Systems Integration Business [Member]

Network Service and Systems Integration Business [Member]

ATM Operation Business [Member]

ATM Operation Business [Member]

ATM Operation Business [Member]

ATM Operation Business [Member]

ATM Operation Business [Member]

ATM Operation Business [Member]

ATM Operation Business [Member]

ATM Operation Business [Member]

Intersegment Eliminations [Member]

Intersegment Eliminations [Member]

Intersegment Eliminations [Member]

Intersegment Eliminations [Member]

Customers [Member]

Customers [Member]

Customers [Member]

Customers [Member]

Intersegment [Member]

Intersegment [Member]

Intersegment [Member]

Intersegment [Member]

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

Customers [Member]

Customers [Member]

Customers [Member]

Customers [Member]

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

Segment Reporting Information [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Revenue

$1,109,655

¥ 114,272,351

¥ 106,248,486

¥ 97,314,605

$1,082,205

¥ 111,445,519

¥ 103,928,400

¥ 95,990,449

$4,428

¥ 455,975

¥ 558,753

¥ 506,030

$1,086,633

¥ 111,901,494

¥ 104,487,153

¥ 96,496,479

$27,450

¥ 2,826,832

¥ 2,320,086

¥ 1,324,156

$27,450

¥ 2,826,832

¥ 2,320,086

¥ 1,324,156

$4,428

¥ 455,975

¥ 558,753

¥ 506,030

Note_20_Business_Segments_Deta2

Note 20 - Business Segments (Details) - Segment Profit or Loss

12 Months Ended

In Thousands, unless otherwise specified

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

Network Service and Systems Integration Business [Member]

Network Service and Systems Integration Business [Member]

Network Service and Systems Integration Business [Member]

Network Service and Systems Integration Business [Member]

ATM Operation Business [Member]

ATM Operation Business [Member]

ATM Operation Business [Member]

ATM Operation Business [Member]

Intersegment Eliminations [Member]

Intersegment Eliminations [Member]

Intersegment Eliminations [Member]

Intersegment Eliminations [Member]

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

Operating income (loss):

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Operating Income (Loss)

$55,577

¥ 5,723,312

¥ 7,752,642

¥ 6,353,483

$51,221

¥ 5,274,753

¥ 7,629,435

¥ 6,631,476

$5,620

¥ 578,794

¥ 239,035

¥ (194,264)

$1,264

¥ 130,235

¥ 115,828

¥ 83,729

Note_20_Business_Segments_Deta3

Note 20 - Business Segments (Details) - Segment Assets	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013
In Thousands, unless otherwise specified	USD ($)	JPY (¥)	JPY (¥)	Network Service and Systems Integration Business [Member]	Network Service and Systems Integration Business [Member]	Network Service and Systems Integration Business [Member]	ATM Operation Business [Member]	ATM Operation Business [Member]	ATM Operation Business [Member]
				USD ($)	JPY (¥)	JPY (¥)	USD ($)	JPY (¥)	JPY (¥)
Segment assets:	'	'	'	'	'	'	'	'	'
Segment assets	$1,008,609	¥ 103,866,575	¥ 82,111,266	$979,417	¥ 100,860,325	¥ 79,958,814	$29,192	¥ 3,006,250	¥ 2,152,452

Note_20_Business_Segments_Deta4

Note 20 - Business Segments (Details) - Other Significant Segment Items

12 Months Ended

In Thousands, unless otherwise specified

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

Network Service and Systems Integration Business [Member]

Network Service and Systems Integration Business [Member]

Network Service and Systems Integration Business [Member]

Network Service and Systems Integration Business [Member]

ATM Operation Business [Member]

ATM Operation Business [Member]

ATM Operation Business [Member]

ATM Operation Business [Member]

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

USD ($)

JPY (¥)

JPY (¥)

JPY (¥)

Segment Reporting Information [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

Depreciation and amortization

$85,677

¥ 8,822,981

¥ 7,507,808

¥ 7,143,631

$81,619

¥ 8,405,080

¥ 7,178,397

¥ 7,006,576

$4,058

¥ 417,901

¥ 329,411

¥ 137,055

Note_21_Advertising_Expenses_D

Note 21 - Advertising Expenses (Details)	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
	USD ($)	JPY (¥)	JPY (¥)	JPY (¥)
Other Income and Expenses [Abstract]	'	'	'	'
Advertising Expense	$6,379	¥ 656,890	¥ 671,260	¥ 563,051

Note_22_Related_Party_Transact2

Note 22 - Related Party Transactions (Details)	Mar. 31, 2014
Note 22 - Related Party Transactions (Details) [Line Items]	'
Percentage Of Voting Shares Owned By NTT Group	26.40%
NTT [Member]	'
Note 22 - Related Party Transactions (Details) [Line Items]	'
Percentage Of Shares Owned By NTT Group	26.00%
Percentage Of Voting Shares Owned By NTT Group	26.40%

Note_22_Related_Party_Transact3

Note 22 - Related Party Transactions (Details) - Related Party Transactions (NTT [Member])	12 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
	USD ($)	JPY (¥)	JPY (¥)	JPY (¥)
Related Party Transaction [Line Items]	'	'	'	'
Accounts receivable	$4,339	¥ 446,857	¥ 171,909	'
Accounts payable	17,702	1,822,997	1,578,969	'
Revenues	23,023	2,370,954	880,079	895,189
Costs	$151,283	¥ 15,579,173	¥ 14,966,177	¥ 14,225,717

Note_23_Subsequent_Events_Deta

Note 23 - Subsequent Events (Details)	0 Months Ended			1 Months Ended			0 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Nov. 08, 2013	Nov. 08, 2012	Nov. 08, 2011	Jun. 26, 2013	Jun. 27, 2012	Jun. 28, 2011	Jun. 25, 2014	Jun. 25, 2014
	JPY (¥)	JPY (¥)	JPY (¥)	JPY (¥)	JPY (¥)	JPY (¥)	Subsequent Event [Member]	Subsequent Event [Member]
							USD ($)	JPY (¥)
Note 23 - Subsequent Events (Details) [Line Items]	'	'	'	'	'	'	'	'
Common Stock, Dividends, Per Share, Declared	¥ 11	¥ 8.75	¥ 7.5	¥ 10	¥ 8.75	¥ 7.5	$0.11	¥ 11
Dividends, Common Stock, Cash	'	'	'	'	'	'	$4,907	¥ 505,330