Nidec (NJDCY) 20-F 26 Jun 14 2013 FY Annual report (foreign) Financial data

Document_and_Entity_Informatio

Document and Entity Information	12 Months Ended
	Mar. 31, 2014
Document Type	'20-F
Amendment Flag	'false
Document Period End Date	31-Mar-14
Document Fiscal Year Focus	'2013
Document Fiscal Period Focus	'FY
Trading Symbol	'NJ
Entity Registrant Name	'NIDEC CORP
Entity Central Index Key	'0001158967
Current Fiscal Year End Date	'--03-31
Entity Well-known Seasoned Issuer	'Yes
Entity Current Reporting Status	'Yes
Entity Filer Category	'Large Accelerated Filer
Entity Common Stock, Shares Outstanding	290,150,160

CONSOLIDATED_BALANCE_SHEETS

CONSOLIDATED BALANCE SHEETS (JPY ¥)	Mar. 31, 2014	Mar. 31, 2013
In Millions, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	¥ 247,740	¥ 193,420
Trade notes and accounts receivable, net of allowance for doubtful accounts of ¥860 million on March 31, 2013 and ¥1,126 million on March 31, 2014:	'	'
Notes	12,188	10,479
Accounts	184,096	148,606
Inventories	123,881	99,826
Other current assets	48,063	48,359
Total current assets	615,968	500,690
Marketable securities and other securities investments	16,437	15,900
Investments in and advances to affiliated companies	2,018	1,160
Long-term Investments, Total	18,455	17,060
Property, plant and equipment:	'	'
Land	47,137	43,523
Buildings	177,617	159,270
Machinery and equipment	363,806	330,425
Construction in progress	18,372	21,837
Property, Plant and Equipment, Gross, Total	606,932	555,055
Less-Accumulated depreciation	-308,051	-277,078
Long-lived assets	298,881	277,977
Goodwill	154,927	132,775
Other non-current assets, net of allowance for doubtful accounts of ¥515 million on March 31, 2013 and ¥467 million on March 31, 2014	77,687	76,915
Total assets	1,165,918	1,005,417
Current liabilities:	'	'
Short-term borrowings	22,600	32,798
Current portion of long-term debt	29,245	133,628
Trade notes and accounts payable	166,383	134,165
Accrued expenses	31,045	31,854
Other current liabilities	33,142	32,432
Total current liabilities	282,415	364,877
Long-term liabilities:	'	'
Long-term debt	299,411	146,271
Accrued pension and severance costs	17,943	19,235
Other long-term liabilities	25,244	21,217
Total long-term liabilities	342,598	186,723
Commitments and contingencies (Notes 21 and 23)	'	'
Equity:	'	'
Common stock authorized 2013 and 2014: 960,000,000 shares; issued: 2013- 290,150,160 shares / 2014- 290,150,160 shares	66,551	66,551
Additional paid-in capital	65,197	70,518
Retained earnings	367,617	322,638
Accumulated other comprehensive income (loss):	'	'
Foreign currency translation adjustments	54,539	12,636
Net unrealized gains and losses on securities	4,185	1,187
Net gains and losses on derivative instruments	-24	242
Pension liability adjustments	-324	-1,112
Treasury stock, at cost: 2013- 20,787,044 shares / 2014- 14,343,952 shares	-39,640	-57,007
Total Nidec Corporation shareholders' equity	518,101	415,653
Noncontrolling interests	22,804	38,164
Total equity	540,905	453,817
Total liabilities and equity	¥ 1,165,918	¥ 1,005,417

CONSOLIDATED_BALANCE_SHEETS_Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) (JPY ¥)	Mar. 31, 2014	Mar. 31, 2013
In Millions, except Share data, unless otherwise specified
Trade notes and accounts receivable, allowance for doubtful accounts	¥ 1,126	¥ 860
Other non-current assets, allowance for doubtful accounts	¥ 467	¥ 515
Common stock, authorized	960,000,000	960,000,000
Common stock, issued	290,150,160	290,150,160
Treasury stock, shares	14,343,952	20,787,044

CONSOLIDATED_STATEMENTS_OF_INC

CONSOLIDATED STATEMENTS OF INCOME (JPY ¥)	12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013	Mar. 31, 2012
Net sales	¥ 875,109		¥ 709,270	¥ 682,320
Operating expenses:	'		'	'
Cost of products sold	674,699		572,634	523,729
Selling, general and administrative expenses	77,534		84,760	55,471
Research and development expenses	37,808		34,278	30,050
Costs and Expenses, Total	790,041		691,672	609,250
Operating income	85,068		17,598	73,070
Other income (expense):	'		'	'
Interest and dividend income	2,376		1,831	1,634
Interest expense	-1,526		-679	-299
Foreign exchange loss, net	-56		-2,973	-1,756
(Loss) gain on marketable securities, net	245		-87	-202
Other, net	-1,443		-2,292	-1,591
Nonoperating Income (Expense), Total	-404		-4,200	-2,214
Income from continuing operations before income taxes	84,664		13,398	70,856
Income taxes	-25,729		-6,562	-18,801
Equity in net income (loss) of affiliated companies	-25		13	0
Income from continuing operations	58,910		6,849	52,055
Loss on discontinued operations	'		'	-7,768
Consolidated net income	58,910		6,849	44,287
Less: Net (income) loss attributable to noncontrolling interests	-2,506		1,137	-3,556
Net income attributable to Nidec Corporation	56,404		7,986	40,731
Earning per share-basic	'		'	'
Income from continuing operations attributable to Nidec Corporation	¥ 207.31		¥ 29.64	¥ 168.16
Loss on discontinued operations attributable to Nidec Corporation	'		'	¥ (20.04)
Net income attributable to Nidec Corporation	¥ 207.31	[1]	¥ 29.64	¥ 148.12
Earning per share-diluted	'		'	'
Income from continuing operations attributable to Nidec Corporation	¥ 193.96		¥ 27.49	¥ 157.2
Loss on discontinued operations attributable to Nidec Corporation	'		'	¥ (18.75)
Net income attributable to Nidec Corporation	¥ 193.96	[1]	¥ 27.49	¥ 138.45
Cash dividends paid	¥ 42.5		¥ 45	¥ 45
Net income attributable to Nidec Corporation	'		'	'
Income from continuing operations attributable to Nidec Corporation	56,404		7,986	46,242
Loss on discontinued operations attributable to Nidec Corporation	'		'	-5,511
Net income attributable to Nidec Corporation	¥ 56,404		¥ 7,986	¥ 40,731
[1]	Earnings-per-share amounts for each quarter are computed independently. As a result, their sum may not equal the total year earnings-per-share amounts.

CONSOLIDATED_STATEMENTS_OF_COM

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Consolidated net income	¥ 58,910	¥ 6,849	¥ 44,287
Other comprehensive income (loss), net of tax	'	'	'
Foreign currency translation adjustments	43,429	62,158	-2,560
Net unrealized gains and losses on securities	2,980	151	-7
Net gains and losses on derivative instruments	-266	169	-146
Pension liability adjustments	737	-433	93
Other comprehensive income (loss), Net-of-tax	46,880	62,045	-2,620
Total comprehensive income (loss)	105,790	68,894	41,667
Less: Comprehensive (income) loss attributable to noncontrolling interests	-3,963	-487	-3,983
Comprehensive income (loss) attributable to Nidec Corporation	¥ 101,827	¥ 68,407	¥ 37,684

CONSOLIDATED_STATEMENTS_OF_CHA

CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (JPY ¥)	Total	Common stock	Additional Paid-in capital	Retained earnings	Accumulated other comprehensive income (loss)	Treasury stock, at cost	Nidec Corporation total shareholders' equity	Non- controlling interests
In Millions, except Share data, unless otherwise specified
Beginning Balance at Mar. 31, 2011	¥ 410,506	¥ 66,551	¥ 66,960	¥ 298,445	¥ (44,421)	¥ (32,285)	¥ 355,250	¥ 55,256
Beginning Balance (in shares) at Mar. 31, 2011	'	290,150,160	'	'	'	'	'	'
Comprehensive income:	'	'	'	'	'	'	'	'
Net income	44,287	'	'	40,731	'	'	40,731	3,556
Other comprehensive income (loss)	'	'	'	'	'	'	'	'
Foreign currency translation adjustments	-2,560	'	'	'	-2,749	'	-2,749	189
Unrealized gains and losses on securities	-7	'	'	'	-53	'	-53	46
Unrealized gains and losses on derivative instruments	-146	'	'	'	-146	'	-146	'
Pension liability adjustments	93	'	'	'	-99	'	-99	192
Total other comprehensive income (loss)	-2,620	'	'	'	'	'	-3,047	427
Total comprehensive income	41,667	'	'	'	'	'	37,684	3,983
Purchase of treasury stock	-10,155	'	'	'	'	-10,155	-10,155	'
Dividends paid to shareholders of Nidec Corporation	-12,399	'	'	-12,399	'	'	-12,399	'
Dividends paid to noncontrolling interests	-1,444	'	'	'	'	'	'	-1,444
Capital transaction with consolidated subsidiaries and other	-2,564	'	-198	'	'	'	-198	-2,366
Ending Balance at Mar. 31, 2012	425,611	66,551	66,762	326,777	-47,468	-42,440	370,182	55,429
Ending Balance (in shares) at Mar. 31, 2012	'	290,150,160	'	'	'	'	'	'
Comprehensive income:	'	'	'	'	'	'	'	'
Net income	6,849	'	'	7,986	'	'	7,986	-1,137
Other comprehensive income (loss)	'	'	'	'	'	'	'	'
Foreign currency translation adjustments	62,158	'	'	'	60,547	'	60,547	1,611
Unrealized gains and losses on securities	151	'	'	'	174	'	174	-23
Unrealized gains and losses on derivative instruments	169	'	'	'	169	'	169	'
Pension liability adjustments	-433	'	'	'	-469	'	-469	36
Total other comprehensive income (loss)	62,045	'	'	'	'	'	60,421	1,624
Total comprehensive income	68,894	'	'	'	'	'	68,407	487
Purchase of treasury stock	-31,277	'	'	'	'	-31,277	-31,277	'
Change in ownership of subsidiaries in connection with share exchange transaction	'	'	3,270	'	'	16,710	19,980	-19,980
Dividends paid to shareholders of Nidec Corporation	-12,125	'	'	-12,125	'	'	-12,125	'
Dividends paid to noncontrolling interests	-1,421	'	'	'	'	'	'	-1,421
Acquisitions of new subsidiaries	3,570	'	'	'	'	'	'	3,570
Capital transaction with consolidated subsidiaries and other	565	'	486	'	'	'	486	79
Ending Balance at Mar. 31, 2013	453,817	66,551	70,518	322,638	12,953	-57,007	415,653	38,164
Ending Balance (in shares) at Mar. 31, 2013	'	290,150,160	'	'	'	'	'	'
Comprehensive income:	'	'	'	'	'	'	'	'
Net income	58,910	'	'	56,404	'	'	56,404	2,506
Other comprehensive income (loss)	'	'	'	'	'	'	'	'
Foreign currency translation adjustments	43,429	'	'	'	41,903	'	41,903	1,526
Unrealized gains and losses on securities	2,980	'	'	'	2,998	'	2,998	-18
Unrealized gains and losses on derivative instruments	-266	'	'	'	-266	'	-266	'
Pension liability adjustments	737	'	'	'	788	'	788	-51
Total other comprehensive income (loss)	46,880	'	'	'	'	'	45,423	1,457
Total comprehensive income	105,790	'	'	'	'	'	101,827	3,963
Purchase of treasury stock	-2,838	'	'	'	'	-2,838	-2,838	'
Change in ownership of subsidiaries in connection with share exchange transaction	'	'	-4,279	'	'	20,655	16,376	-16,376
Dividends paid to shareholders of Nidec Corporation	-11,425	'	'	-11,425	'	'	-11,425	'
Dividends paid to noncontrolling interests	-894	'	'	'	'	'	'	-894
Capital transaction with consolidated subsidiaries and other	-3,545	'	-1,042	'	'	-450	-1,492	-2,053
Ending Balance at Mar. 31, 2014	¥ 540,905	¥ 66,551	¥ 65,197	¥ 367,617	¥ 58,376	¥ (39,640)	¥ 518,101	¥ 22,804
Ending Balance (in shares) at Mar. 31, 2014	'	290,150,160	'	'	'	'	'	'

CONSOLIDATED_STATEMENTS_OF_CAS

CONSOLIDATED STATEMENTS OF CASH FLOWS (JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:	'	'	'
Consolidated net income	¥ 58,910	¥ 6,849	¥ 44,287
Adjustments to reconcile net income to net cash provided by operating activities:	'	'	'
Depreciation	39,485	34,935	31,511
Amortization	6,797	4,785	2,819
Loss (gain) on marketable securities, net	-245	87	200
Loss on sales, disposal or impairment of property, plant and equipment	534	10,300	15,705
Loss recovery and gain on property, plant and equipment damaged in flood	-62	-4,027	-19,662
Deferred income taxes	9,217	-12,055	12,835
Equity in net (income) loss of affiliated companies	25	-13	0
Foreign currency adjustments	-3,498	1,744	236
Accrual for pension and severance costs, net payments	-4,241	-396	-915
Changes in operating assets and liabilities:	'	'	'
(Increase) decrease in notes and accounts receivable	-19,957	53,221	-14,819
(Increase) decrease in inventories	-10,244	14,090	-257
(Decrease) increase in notes and accounts payable	14,299	-1,257	-8,061
(Decrease) increase in accrued income taxes	3,899	-7,263	-2,259
Other	-7,700	9,286	-4,908
Net cash provided by operating activities	87,219	110,286	56,712
Cash flows from investing activities:	'	'	'
Additions to property, plant and equipment	-40,297	-61,368	-41,446
Proceeds from sales of property, plant and equipment	2,601	1,036	2,725
Insurance proceeds related to property, plant and equipment damaged in flood	2,772	880	20,804
Purchases of marketable securities	-309	-147	-213
Proceeds from sales or redemption of marketable securities	1,059	692	414
Acquisitions of business, net of cash acquired	-23,350	-79,884	5,201
Other	-5,654	4,937	-7,403
Net cash used in investing activities	-63,178	-133,854	-19,918
Cash flows from financing activities:	'	'	'
Increase (decrease) in short-term borrowings	-11,821	-52,199	26,060
Proceeds from issuance of long-term debt	30,000	71,307	'
Repayments of long-term debt	-34,323	-12,392	-1,229
Proceeds from issuance of corporate bonds	50,000	100,000	'
Redemption of corporate bonds	-4,250	'	'
Purchases of treasury stock	-2,838	-31,277	-10,155
Payments for additional investments in subsidiaries	-217	-92	-454
Dividends paid to shareholders of Nidec Corporation	-11,425	-12,125	-12,399
Dividends paid to noncontrolling interests	-894	-1,421	-1,444
Other	-761	-684	-1,193
Net cash (used in) provided by financing activities	13,471	61,117	-814
Effect of exchange rate changes on cash and cash equivalents	16,808	25,581	-11
Net increase in cash and cash equivalents	54,320	63,130	35,969
Cash and cash equivalents at beginning of year	193,420	130,290	94,321
Cash and cash equivalents at end of year	¥ 247,740	¥ 193,420	¥ 130,290

Nature_of_operations

Nature of operations	12 Months Ended
	Mar. 31, 2014
Nature of operations	'
	1. Nature of operations:
	NIDEC Corporation (the “Company”) and its subsidiaries (collectively “NIDEC”) are primarily engaged in the design, development, manufacture and marketing of i) small precision motors, which include spindle motors for hard disk drives, motors for optical disk drives, small precision fans, motor appliances and other small motors; ii) automotive, appliance, commercial and industrial products, which are used in various electric household appliances, commercial and industrial equipment and automobiles; iii) machinery, which includes, test systems, measuring equipment, power transmission equipment, factory automation systems, press machines, card readers and industrial robots; iv) electronic and optical components, which include camera shutters, camera lens units, switches, trimmer potentiometers, processing and precision plastic mold products; and v) other products, which include other services. Manufacturing operations are located primarily in Asia (China, Thailand, Vietnam and the Philippines), North America and Japan, and sales subsidiaries are primarily located in Asia, Japan, North America and Europe.
	The main customers for NIDEC are manufacturers of hard disk drives. NIDEC also sells its products to the manufacturers of various electric household appliances, automation equipment, automotive components, home video game consoles, telecommunication equipment and audio-visual equipment.

Summary_of_significant_account

Summary of significant accounting policies	12 Months Ended
	Mar. 31, 2014
Summary of significant accounting policies	'
	2. Summary of significant accounting policies:
	The Company and its subsidiaries in Japan maintain their records and prepare their financial statements in accordance with accounting principles generally accepted in Japan, and its foreign subsidiaries in conformity with those of their countries of domicile. Certain adjustments and reclassifications have been incorporated in the accompanying consolidated financial statements to conform with accounting principles generally accepted in the United States of America. Significant accounting policies after reflecting adjustments for the above are as follows:
	Estimates -
	The preparation of NIDEC’s consolidated financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and contingent assets and liabilities at the date of the financial statements, as well as the reported amounts of revenues and expenses during the reporting period. Some of the more significant estimates include the valuation of inventories, allowance for doubtful accounts, depreciation and amortization of long-lived assets, valuation allowance for deferred tax assets, valuation of investment securities, fair value of financial instruments, uncertain tax positions, pension liabilities, the recoverability of long-lived assets and goodwill, and fair value of assets acquired and liabilities assumed. Actual results could differ from those estimates.
	Basis of consolidation and accounting for investments in affiliated companies -
	The consolidated financial statements include the accounts of the Company and those of its majority-owned subsidiary companies. All significant intercompany transactions and accounts have been eliminated. Companies over which NIDEC exercises significant influence, but which it does not control, are classified as affiliated companies and accounted for using the equity method. Consolidated net income includes NIDEC’s equity in current earnings (losses) of such companies, after elimination of unrealized intercompany profits.
	On occasion, NIDEC may acquire additional shares of the voting rights of a consolidated subsidiary or dispose of a part of those shares or a Nidec consolidated subsidiary may issue its shares to third parties. With respect to such transactions, all transactions for changes in a parent’s ownership interest in a subsidiary that do not result in the subsidiary ceasing to be a subsidiary are recognized as equity transactions.
	Translation of foreign currencies -
	Non monetary asset and liability accounts of foreign subsidiaries and affiliates are translated into Japanese yen at the year-end exchange rates and all income and expense accounts are translated at exchange rates that approximate those prevailing at the time of the transactions. The resulting translation adjustments are included as a component of accumulated other comprehensive income in shareholders’ equity.
	Monetary assets and liabilities denominated in foreign currencies are translated at the year-end exchange rates and the resulting transaction gains or losses are taken into income.
	Cash and cash equivalents -
	Cash and cash equivalents include all highly liquid investments, with original maturities of three months or less that are readily convertible to known amounts of cash and are so near maturity that they present insignificant risk of changes in value because of changes in interest rates.
	Inventories -
	Inventories are stated at the lower of cost or market. Cost is determined principally on the weighted average cost basis. Cost includes the cost of materials, labor and applied factory overhead. Projects in progress, which mainly relate to production of factory automation equipment based on contracts with customers, are stated at the lower of cost or market, cost being determined as the accumulated production cost.
	Marketable securities -
	Marketable securities consist of equity securities that are listed on recognized stock exchanges and debt securities. Equity securities designated as available-for-sale are carried at fair value with changes in unrealized gains or losses included as a component of accumulated other comprehensive income in shareholders’ equity, net of applicable taxes. Realized gains and losses are determined on the average cost method and are reflected in the statement of income. Other than temporary declines in market value of individual securities classified as available-for-sale are charged to income in the period the loss occurs. Debt securities designated as held-to-maturity securities are recorded at amortized cost, adjusted for the amortization or accretion of premiums or discounts.
	Derivative financial instruments -
	NIDEC manages the exposures of fluctuations in foreign exchange rate, interest rate and commodity prices through the use of derivative financial instruments which include foreign exchange forward contracts, currency option contracts, interest rate swap agreements and commodity future contracts. NIDEC does not hold derivative financial instruments for trading purposes.
	Derivatives are accounted for under ASC 815, “Derivatives and Hedging.” All derivatives are recorded as either assets or liabilities on the balance sheet and measured at fair value. Changes in the fair value of derivatives are charged in current earnings. However certain derivatives may qualify for hedge accounting as a cash flow hedge, if the hedging relationship is expected to be highly effective in achieving offsetting of cash flows of the hedging instruments and hedged items. Under hedge accounting, changes in the fair value of the effective portion of these derivatives designated as cash flow hedge derivatives are deferred in accumulated other comprehensive income and charged to earnings when the underlying transaction being hedged occurs.
	NIDEC designates certain foreign exchange forward contracts, interest rate swap agreements and commodity future contracts as cash flow hedges. NIDEC formally documents all relationships between hedging instruments and hedged items, as well as its risk management objective and strategy for undertaking various hedge transactions. This process includes linking all derivatives designated as cash flow hedges to specific assets and liabilities on the balance sheet or forecasted transactions. NIDEC also formally assesses, both at the hedge’s inception and on an ongoing basis, whether the derivatives that are used in hedging transactions are highly effective in offsetting cash flows of hedged items. When it is determined that a derivative is not a highly effective hedge or that it has ceased to be a highly effective hedge, NIDEC discontinues hedge accounting prospectively. When a cash flow hedge is discontinued, the previously recognized net derivative gains or losses remain in accumulated other comprehensive income until the hedged transaction occurs, unless it is probable that the forecasted transaction will not occur at which point the derivative gains or losses are reclassified into earnings immediately.
	Property, plant and equipment -
	Property, plant and equipment are stated at cost. Major renewals and improvements are capitalized; minor replacements, maintenance and repairs are charged to expense in the year incurred.
	Depreciation of property, plant and equipment is computed on the straight-line method at rates based on the estimated useful lives of the assets. Estimated useful lives range from 7 to 47 years for factories to produce NIDEC’s products, 50 years for the head office and sales offices, from 3 to 18 years for leasehold improvements, and from 2 to 15 years for machinery and equipment.
	Depreciation expense amounted to ¥31,511 million, ¥34,935 million, and ¥39,485 million for the years ended March 31, 2012, 2013 and 2014, respectively.
	Lease-
	NIDEC capitalizes leases and related obligations when any of the four criteria are met within the guidance of ASC 840 “Leases”. Under ASC840, these leases and related obligations are capitalized at the commencement of the lease at the lower of the fair value of the leased property and the present value of the minimum lease payments.
	Goodwill and other intangible assets -
	Goodwill and other intangible assets are accounted for under ASC350, “Intangibles—Goodwill and Other”.
	Goodwill acquired in business combinations is not amortized but tested annually for impairment. NIDEC tests for impairment at the reporting unit level on January 1st of each year. In addition, NIDEC tests for impairment between annual tests if an event occurs or circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying amount. This test is a two-step process. The first step of the goodwill impairment test, used to identify potential impairment, compares the fair value of the reporting unit with its carrying amount, including goodwill. If the fair value, which is based on discounted future cash flows, exceeds the carrying amount, goodwill is not considered impaired. If the carrying amount exceeds the fair value, the second step must be performed to measure the amount of the impairment loss, if any. The second step compares the implied fair value of the reporting unit’s goodwill with the carrying amount of that goodwill.
	Other intangible assets include proprietary technology and customer relationships, as well as software and other intangible assets acquired in business combinations. Intangible assets with an indefinite life are not subject to amortization and are tested for impairment once on January 1st of each year or more frequently if an event occurs or circumstances change. Intangible assets with a definite life are amortized on a straight-line basis over their estimated useful lives. The weighted average amortization period for proprietary technology, customer relationships and software are 12 years, 18 years and 5 years, respectively.
	Long-lived assets -
	NIDEC reviews its long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset group may not be recoverable. An impairment loss would be recognized when the carrying amount of an asset group exceeds the estimated undiscounted future cash flows expected to result from the use of the asset group and its eventual disposition. The amount of the impairment loss to be recorded is calculated as the excess of the assets group’s carrying value over its fair value. Long-lived assets that are to be disposed of other than by sale are considered to be held and used until the disposal. Long-lived assets that are to be disposed of by sale are reported at the lower of their carrying value or fair value less costs to sell. Reductions in carrying value are recognized in the period in which long-lived assets are classified as held for sale.
	Revenue recognition -
	NIDEC recognizes revenue when persuasive evidence of an arrangement exists, delivery has occurred, the sales price is fixed or determinable and collectibility is reasonably assured. For small precision motors, automotive, appliance, commercial and industrial products and electronic and optical components, these criteria are generally met at the time a product is delivered to the customers’ site which is the time the customer has taken title to the product and the risk and rewards of ownership have been substantively transferred. These conditions are met at the time of delivery to customers in domestic sales (FOB destination) and at the time of shipment for export sales (FOB shipping point). Revenue for machinery sales is recognized upon receipt of final customer acceptance. At the time the related revenue is recognized, NIDEC makes provisions for estimated product returns. Revenue from a part of sales of automotive, appliance, commercial and industrial products under long-term construction type arrangements are recognized under the percentage-of-completion method. Under the percentage-of-completion method, revenue is recognized as a percentage of estimated total revenue that incurred costs to date bear to estimated total costs after giving effect to estimates of costs to complete based upon the most recent information.
	Research and development expenses -
	Research and development expenses, mainly consisting of personnel and depreciation expenses at research and development branches, are charged to operations as incurred.
	Advertising costs -
	Advertising and sales promotion costs are expensed as incurred. Advertising costs were ¥228 million, ¥296 million, and ¥477 million for the years ended March 31, 2012, 2013 and 2014, respectively.
	Income taxes -
	The provision for income taxes is computed based on the pretax income included in the consolidated statement of income. The asset and liability approach is used to recognize deferred tax assets and liabilities for the expected future tax consequences of temporary differences between the carrying amounts and the tax bases of assets and liabilities. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. Valuation allowances are recorded to reduce deferred tax assets when it is more likely than not that a tax benefit will not be realized.
	NIDEC recognizes the financial statement effects of tax positions when it is 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 percent likely of being realized upon settlement. Interest and penalties accrued related to unrecognized tax benefits are included in other, net in the consolidated statements of income.
	Earnings per share -
	Basic net income per common share is calculated by dividing net income by the weighted-average number of shares outstanding during the reported period. The calculation of diluted net income per common share is similar to the calculation of basic net income per share, except that the weighted-average number of shares outstanding includes the additional dilution from potential common stock equivalents such as convertible bonds and options.
	Reclassification
	Certain reclassifications of previously reported amounts have been made to the consolidated statements of income and cash flows for the years ended March 31, 2012 and 2013 to conform to the current year presentation.
	As of March 31, 2012, NIDEC discontinued its lens actuator business and its tape drive and disk drive mechanism business included within the Nidec Sankyo reportable segment, and its compact digital camera lens unit business included within the Nidec Copal reportable segment. The operating results of the discontinued businesses and exit costs with related taxes were recorded as “Loss on discontinued operations” in the consolidated statement of income in accordance with ASC 205-20, “Presentation of Financial Statements-Discontinued Operations”.
	Accounting Changes
	As of April 1, 2013, NIDEC adopted FASB Accounting Standards Codification™ (ASC) 350 “Intangibles-Goodwill and Other” updated by Accounting Standards Update (ASU) No. 2012-02 “Testing Indefinite-Lived Intangible Assets for Impairment.” ASU 2012-02 allows an entity the option of performing a qualitative assessment before calculating the fair value of an indefinite-lived intangible asset and performing the quantitative impairment test. If an entity determines, on the basis of qualitative factors, that it is more likely than not that the asset is impaired, the quantitative impairment test would be required. The adoption of this standard did not have material impact on NIDEC’s consolidated financial position, results of operations and liquidity.
	As of April 1, 2013, NIDEC adopted FASB ASC 220 “Comprehensive income.” updated by ASU No. 2013-02 “Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income.” ASU 2013-02 requires an entity 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 but only if the amount reclassified is required under U.S. GAAP to be reclassified to net income in its entirety in the same reporting period. The standard is provision for disclosure. The adoption of this standard did not have any impact on NIDEC’s consolidated financial position, results of operations and liquidity.
	Recent Accounting Pronouncements to be adopted in future periods
	In July 2013, the FASB issued ASU No. 2013-11, “Income taxes (Topic 740): Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists.” ASU 2013-11 clarifies that an unrecognized tax benefit, or a portion of an unrecognized tax benefit, should be presented in the financial statements as a reduction to a deferred tax asset for a net operating loss carryforward, a similar tax loss, or a tax credit carryforward if such settlement is required or expected in the event the uncertain tax position is disallowed. In situations where a net operating loss carry forward, a similar tax loss, or a tax credit carryforward is not available at the reporting date under the tax law of the applicable jurisdiction or the tax of the jurisdiction does not require, and the entity does not intend to use, the deferred tax asset for such purpose, the unrecognized tax benefit should be presented in the financial statements as a liability and should not be combined with deferred tax assets. ASU 2013-11 is effective for reporting periods beginning after December 15, 2013. Early adoption and retrospective application are permitted. This standard is provision for disclosure. The adoption of this standard will not have any impact on NIDEC’s consolidated financial position, results of operations or liquidity.
	In April 2014, the FASB issued ASU No. 2014-08, “Presentation of Financial Statements (Topic 205) and Property, Plant, and Equipment (Topic 360): “Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity.” Under the new standard, a disposal of a component or a group of components of an entity is required to be reported in discontinued operations if the disposal represents a strategic shift that has (or will have) a major effect on an entity’s operations and financial results when the component meets the criteria to be classified as held for sale or is disposed. The amendments in this update also require additional disclosures about discontinued operations and disposal of an individually significant component of an entity that does not qualify for discontinued operations. ASU 2014-08 is effective for annual and interim periods beginning after December 15, 2014. Early adoption is permitted. The impact of the adoption of ASU 2014-08 on NIDEC’s consolidated financial position, results of operations and liquidity will depend on, and may be significant depending on, the size and nature of its future disposal.
	In May 2014, the FASB issued ASU No. 2014-09, “Revenue from Contracts with Customers (Topic 606)” Under the new standard, an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. An entity should recognize revenue when (or as) it satisfies a performance obligation by transferring a promised good or service to a customer, and the transaction price should be allocated to performance obligation in the contract. The new standard also requires an entity to disclose sufficient information to enable users of financial statements to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. ASU 2014-09 is effective for annual and interim periods beginning after December 15, 2016. Early application is not permitted. NIDEC is currently evaluating the potential impact from adopting ASU 2014-09 on its consolidated financial position, results of operations and liquidity.

Acquisitions

Acquisitions	12 Months Ended
	Mar. 31, 2014
Acquisitions	'
	3. Acquisitions
	On July 1, 2011, NIDEC acquired all of the voting rights of Sanyo Seimitsu Co., Ltd. which consists of small precision motor product category, particularly vibration motors for mobile phones of Sanyo Electric Co., Ltd., in order to further develop and expand our small precision motor product category by effectively using the operational resources of, and efficiently developing new products and expanding sales opportunities for small precision motor product category. Sanyo Seimitsu Co., Ltd. was subsequently renamed Nidec Seimitsu Corporation. This acquisition did not have a material impact on NIDEC’s consolidated financial position, results of operations or liquidity.
	On April 2, 2012, NIDEC acquired all of the voting rights in The Minster Machine Company (“Minster”), which consists of machinery product category, particularly medium-sized and large-sized high-speed, high-rigidity press machines and large-sized press machines for dies for motor parts for cash of ¥9,202 million, in order to continue to pursue NIDEC’s group-wide growth strategy by seeking to increase sales by expanding our business not only in NIDEC’s existing electronic parts market but also in wider markets, including the beverage can and automobile parts markets. The Minster Machine Company was subsequently renamed Nidec Minster Corporation.
	On May 31, 2012, NIDEC acquired all of the voting rights in Ansaldo Sistemi Industriali S.p.A. (“Nidec ASI”), an Italian company, which consists of automotive, appliance, commercial and industrial products business for cash of ¥36,564 million, where NIDEC has increasingly focused our efforts as one of the principal growth area, in order to accelerate the global expansion of NIDEC’s industrial motor business by gaining sales platforms in markets where NIDEC currently does not have significant sales and by expanding NIDEC’s product offering to include a wide range of products that are currently not in our product portfolio. Ansaldo Sistemi Industriali S.p.A was subsequently renamed Nidec ASI S.p.A.
	On September 28, 2012, NIDEC acquired all of the voting rights in Avtron Industrial Automation, Inc. (“Avtron”), which consists of rich system engineering resources, experience, the customer relationship and a sales channel in North America for cash of ¥4,861 million, in order to strengthen the industrial motor and automation solutions business and accelerate our strategy to achieve synergies with acquired companies.
	On October 2, 2012, NIDEC acquired 51.4% of the voting rights of SCD Co., Ltd. (“SCD”), a South Korean company, which consists of development, manufacturing and sale of motor drive units for refrigerators and motors for air conditioners for cash of ¥3,305 million, in order to gain an opportunity to enter into business with South Korean home appliance manufacturers that have a strong presence in emerging economies, and seek to expand sales of its rich product line-up.
	On November 1, 2012, NIDEC acquired all of the voting rights in Kinetek Group Inc. (“Kinetek”), which conducts its commercial motor business on a global basis and occupies a leading position in various markets for commercial motors used in such end-products as elevators/escalators, commercial food refrigerators, floor care equipment, golf and utility vehicles, material handling vehicles and aerial lifts for cash of ¥35,697 million, in order to strengthen NIDEC’s commercial motor business.
	On December 28, 2012, NIDEC acquired 51.0% of the voting rights of Nidec Kaiyu Auto Electric (Jiangsu) Co., Ltd. (“Kaiyu”), a Chinese company, which consists of development, manufacturing and sale of brush motors for electric power steering (“EPS”) systems and automotive fans for cash of ¥1,018 million, in order to acquire technologies for brush motors for EPS systems, which NIDEC currently does not possess, and business opportunities in the Chinese automobile market, new entry into which has been difficult.
	On January 1, 2014, NIDEC acquired all of the voting rights in Mitsubishi Materials C.M.I. Corporation (“CMI”), a Japanese company, which consists of development, manufacturing and sale of small motors, electric contact products and other products for cash of ¥5,228 million, in order to strengthen our automotive product business and enhance our product portfolio.
	On March 31, 2014, NIDEC acquired all of the voting rights in Honda Elesys Co., Ltd. (“Elesys”), a Japanese company, which consists of development, manufacturing and sale of automobile electronic control units for car bodies for cash of ¥24,320 million, mainly in order to combine our EPS motors with Elesys’ electronic control units (ECU) to be transformed into a module business, and create sales synergies by utilizing Nidec Group’s sales network for automotive motors.
	The following table summarizes the estimated fair values of the assets acquired and liabilities assumed at the acquisition date.
		Yen in millions
		January 1,			March 31,
		2014			2014
		CMI			Elesys
	Cash and cash equivalents	¥	1,081		¥	5,759
	Accounts receivable		1,323			5,176
	Inventories		2,155			4,600
	Other current assets		683			1,483
	Property, plant and equipment		4,538			6,803
	Goodwill		2,114			9,668
	Intangible assets		55			58
	Other non-current assets		790			657
	Total assets acquired		12,739			34,204
	Accounts payable		(1,420	)		(6,618	)
	Other current liabilities		(2,834	)		(2,417	)
	Other non-current liabilities		(3,256	)		(849	)
	Total liabilities assumed		(7,510	)		(9,884	)
	Noncontrolling interests		(1	)		—
	Net assets acquired	¥	5,228		¥	24,320
	Pursuant to ASC 805 “Business Combinations,” previous year’s consolidated financial statements have been retrospectively adjusted to reflect our valuation of the fair values of the assets acquired and the liabilities assumed upon the acquisition of SCD and Kaiyu in the fiscal year ended March 31, 2013. During the three months ended September 30, 2013, NIDEC completed our valuation of such assets and liabilities of SCD and Kaiyu.
	In addition, NIDEC is currently evaluating the fair values of the assets acquired and the liabilities assumed upon the acquisitions of CMI and Elesys. These assets and liabilities have been recorded on our consolidated balance sheet based on preliminary management estimation as of March 31, 2014. We continue to gather information to evaluate primarily property, plant and equipment and intangible assets that we have acquired.
	Operating Segment	Yen in millions
		Amount of Goodwill			Amount of Goodwill
					deductible for tax
					purposes
	Nidec Sankyo	¥	2,114		¥	334
	All Others		9,668			393
	Total	¥	11,782		¥	727
	Acquisition-related cost of ¥147 million was included in selling, general and administrative expenses in the consolidated statement of income for the year ended March 31, 2014.
	The following represents the unaudited pro forma results of operations of NIDEC for the years ended March 31, 2013 and 2014, as if the acquisition in these companies had occurred on April 1, 2012. The unaudited pro forma results of operations are presented for comparative purposes only and are not necessarily indicative of the results of operations that may occur in the future or that would have occurred had the acquisitions been in effect on the dates indicated.
		Yen in millions
		For the year ended March 31
		(Unaudited)
		2013			2014
	Pro forma net sales	¥	787,716		¥	928,910
	Pro forma net income		9,378			57,788
		Yen
	Pro forma net income attributable to Nidec Corporation per share
	—basic	¥	34,81		¥	212.4
	—diluted		32.32			198.72
	Note: NIDEC implemented a two-for-one stock split on our common stock as of April 1, 2014. Each pro forma net income attributable to Nidec Corporation per share has been adjusted to reflect the effect of the stock split.

Goodwill_and_other_intangible_

Goodwill and other intangible assets	12 Months Ended
	Mar. 31, 2014
Goodwill and other intangible assets	'
	4. Goodwill and other intangible assets:
	Intangible assets subject to amortization are summarized as follows:
		Yen in millions
		March 31
		2013						2014
		Gross		Accumulated		Carrying		Gross			Accumulated		Carrying
		carrying		amortization		amounts		carrying			amortization		amounts
		amounts						amounts
	Proprietary technology	¥	10,017	¥	1,469	¥	8,548	¥	11,671		¥	2,535	¥	9,136
	Customer relationships		43,305		5,817		37,488		48,157			9,626		38,531
	Software		13,830		6,878		6,952		18,001			8,625		9,376
	Other		5,718		1,925		3,793		6,988			3,345		3,643
	Total	¥	72,870	¥	16,089	¥	56,781	¥	84,817		¥	24,131	¥	60,686
	The weighted average amortization periods for proprietary technology, customer relationships and software are 12 years, 18 years and 5 years, respectively.
	Total amortization of intangible assets for the years ended March 31, 2012, 2013 and 2014 amounted to ¥2,664 million, ¥4,627 million and ¥6,377 million, respectively.
	Total indefinite lived intangible assets amounted to ¥7,208 million and ¥7,920 million as of March 31, 2013 and 2014, respectively.
	The estimated aggregate amortization expense for intangible assets for the next five years is as follows:
	Years ending March 31,	Yen in millions
	2015	¥	6,773
	2016		6,445
	2017		5,767
	2018		5,123
	2019		4,656
	NIDEC has completed the annual impairment test for existing goodwill and indefinite lived intangible assets as required by ASC 350 as of January 1, 2014. For the years ended March 31, 2012, 2013 and 2014, NIDEC has determined that the fair value of each reporting unit which includes goodwill has been in excess of its carrying amount. Accordingly, for the years ended March 31, 2012, 2013 and 2014, no goodwill impairment loss has been recorded. As a result of the annual impairment test for existing indefinite lived intangible assets, for the years ended March 31, 2012, 2013 and 2014, impairment loss of indefinite lived intangible assets has not been recorded.
	The changes in the carrying amount of goodwill by operating reportable segment for the years ended March 31, 2012 and 2013 are as follows:
		Yen in millions
		Balance as of		Acquisition		Impairment		Translation			Balance as of
		April 1,				loss		adjustments			March 31,
		2012						and Others			2013
	Goodwill:
	Nidec Electronics (Thailand)	¥	6,109	¥	—	¥	—	¥	885		¥	6,994
	Nidec (Zhejiang)		912		—		—		132			1,044
	Nidec Sankyo		26,100		1,094		—		118			27,312
	Nidec Copal		16,462		—		—		—			16,462
	Nidec Tosok		1,107		—		—		(69	)		1,038
	Nidec Copal Electronics		6,561		—		—		—			6,561
	Nidec Techno Motor		2,049		—		—		—			2,049
	Nidec Motor		11,984		34,021		—		9,003			55,008
	Nidec Motors & Actuators		4,737		1,062		—		586			6,385
	All Others		4,504		4,785		—		633			9,922
		¥	80,525	¥	40,962	¥	—	¥	11,288		¥	132,775
	The changes in the carrying amount of goodwill by operating reportable segment for the years ended March 31, 2013 and 2014 are as follows:
		Yen in millions
		Balance as of		Acquisition		Impairment		Translation			Balance as of
		April 1,				loss		adjustments			March 31,
		2013						and Others			2014
	Goodwill:
	Nidec Electronics (Thailand)	¥	6,994	¥	—	¥	—	¥	651		¥	7,645
	Nidec (Zhejiang)		1,044		—		—		98			1,142
	Nidec Sankyo		27,312		2,114		—		107			29,533
	Nidec Copal		16,462		—		—		—			16,462
	Nidec Tosok		1,038		—		—		—			1,038
	Nidec Copal Electronics		6,561		—		—		—			6,561
	Nidec Techno Motor		2,049		—		—		—			2,049
	Nidec Motor		55,008		—		—		8,070			63,078
	Nidec Motors & Actuators		6,385		—		—		933			7,318
	All Others		9,922		9,668		—		511			20,101
		¥	132,775	¥	11,782	¥	—	¥	10,370		¥	154,927

Supplemental_cash_flow_informa

Supplemental cash flow information	12 Months Ended
	Mar. 31, 2014
Supplemental cash flow information	'
	5. Supplemental cash flow information:
	The supplemental information associated with the consolidated statements of cash flows for the years ended March 31, 2012, 2013 and 2014 are as follows:
		Yen in millions
		For the year  ended
		March 31
		2012		2013		2014
	Cash paid during the fiscal year for:
	Income taxes	¥	8,197	¥	25,879	¥	12,613
	Interest		327		395		1,636
	Non-cash investing and financing activities:
	Capital leasing receivables		31		—		—
	Capital lease obligations		214		206		499
	Change in ownership of subsidiaries in connection with share exchange transaction
	—Change in common stock		—		3,270		4,279
	—Change in treasury stock		—		16,710		20,655

Allowance_for_doubtful_account

Allowance for doubtful accounts	12 Months Ended
	Mar. 31, 2014
Allowance for doubtful accounts	'
	6. Allowance for doubtful accounts:
	NIDEC estimates losses for uncollectible accounts based on historical experience and the evaluation of the likelihood of success in collecting specific customer receivables.
	An analysis of activity within the allowance for doubtful accounts for the years ended March 31, 2012, 2013 and 2014 are as follows:
		Yen in millions
		2012			2013			2014
	Allowance for doubtful accounts at beginning of the year	¥	1,013		¥	1,002		¥	1,375
	Provision for doubtful accounts, net of reversal		30			166			366
	Write-offs		(30	)		(90	)		(267	)
	Translation adjustment and other		(11	)		297			119
	Allowance for doubtful accounts at the end of the year	¥	1,002		¥	1,375		¥	1,593

Inventories

Inventories	12 Months Ended
	Mar. 31, 2014
Inventories	'
	7. Inventories:
	Inventories consist of the following:
		Yen in millions
		March 31
		2013		2014
	Finished goods	¥	42,599	¥	51,293
	Raw materials		30,839		39,993
	Work in process		23,526		28,926
	Supplies and other		2,862		3,669
		¥	99,826	¥	123,881

Other_current_assets

Other current assets	12 Months Ended
	Mar. 31, 2014
Other current assets	'
	8. Other current assets:
	Other current assets as of March 31, 2013 and 2014 consist of the following:
		Yen in millions
		March 31
		2013		2014
	Other receivable	¥	13,740	¥	13,906
	Deferred tax assets (Note 16)		12,787		10,434
	Costs on uncompleted construction contracts		5,799		9,572
	Prepaid expenses		4,079		5,225
	Other		11,954		8,926
		¥	48,359	¥	48,063
	“Other” primarily consists of taxes receivable.

Marketable_securities_and_othe

Marketable securities and other securities investments	12 Months Ended
	Mar. 31, 2014
Marketable securities and other securities investments	'
	9. Marketable securities and other securities investments:
	Marketable securities and other securities investments include debt and equity securities of which the aggregate fair value, gross unrealized gains and losses and cost are as follows:
		Yen in millions
		March 31, 2013
		Cost		Gross		Gross		Fair
				unrealized		unrealized		value
				gains		losses
	Available-for-sale
	Equity securities	¥	7,838	¥	5,814	¥	3	¥	13,649
	Debt securities		405		11		5		411
	Held-to-maturity
	Japanese government debt securities		301		3		—		304
		¥	8,544	¥	5,828	¥	8	¥	14,364
	Securities not practicable to estimate fair value
	Equity securities	¥	1,539
		Yen in millions
		March 31, 2014
		Cost		Gross		Gross		Fair
				unrealized		unrealized		value
				gains		losses
	Available-for-sale
	Equity securities	¥	7,652	¥	6,731	¥	0	¥	14,383
	Debt securities		—		—		—		—
	Held-to-maturity
	Japanese government debt securities		400		2		—		402
		¥	8,052	¥	6,733	¥	0	¥	14,785
	Securities not practicable to estimate fair value
	Equity securities	¥	1,654
	During the years ended March 31, 2012, 2013 and 2014, the net unrealized gain on available-for-sale securities included as a component of accumulated other comprehensive income, net of applicable taxes, decreased by ¥53 million, increased by ¥174 million and increased by ¥2,998 million, respectively.
	Proceeds from sale or redemption of marketable securities were ¥100 million, ¥692 million and ¥1,059 million for the years ended March 31, 2012, 2013 and 2014, respectively. On those sales, gross realized gains were ¥0 million, ¥347 million and ¥242 million and gross realized losses were ¥0 million, ¥0 million and ¥12 million, respectively.
	NIDEC holds long-term investment securities that are classified as “marketable securities and other securities investments.” The securities issued by various non-public companies are recorded at cost, as their fair values are not readily determinable. NIDEC’s management employs a systematic methodology to assess the recoverability of such investments by reviewing the financial position of the underlying companies and the prevailing market conditions in which these companies operate to determine if NIDEC’s investment in each individual company is impaired and whether the impairment is other-than-temporary. If any impairment is assessed to be other-than-temporary, the cost of the investment is written-down by the impaired amount and the amount is recognized as a realized loss for the reporting period which the assessment is made.
	The following tables present the gross unrealized losses on, and fair value of, NIDEC’s investment securities, aggregated by investment category and length of time that individual investment securities have been in a continuous unrealized loss position.
		Yen in millions
		March 31, 2013
		Less than 12 months				12 months or more
		Fair value		Unrealized		Fair value		Unrealized
				loss				loss
	Equity securities	¥	16	¥	1	¥	23	¥	2
	Debt securities		182		5		—		—
		¥	198	¥	6	¥	23	¥	2
		Yen in millions
		March 31, 2014
		Less than 12 months				12 months or more
		Fair value		Unrealized		Fair value		Unrealized
				loss				loss
	Equity securities	¥	0	¥	0	¥	1	¥	0
	Debt securities		—		—		—		—
		¥	0	¥	0	¥	1	¥	0
	NIDEC presumes the value of investment securities is impaired if the fair value is below the original cost. Among the impaired investment securities, NIDEC presumes a decline in value of debt and equity securities is other-than-temporary if the fair value is significantly below the original cost for an extended period of time. The presumption of an other-than-temporary impairment may be overcome if there is evidence to support that the decline is temporary in nature due to the existence of other factors which overcome the duration or magnitude of the decline. On the other hand, even if a fair value is not significantly less than the original cost, the value of investment securities is impaired when specific factors indicate the decline in the fair value is other-than-temporary.
	For the years ended March 31, 2013 and 2014, held-to-maturity securities of ¥301 million and ¥400 million were pledged as collateral for the deferred payments of certain taxes based on the Japanese Custom Act and Consumption Tax Law, respectively.

Other_noncurrent_assets

Other non-current assets	12 Months Ended
	Mar. 31, 2014
Other non-current assets	'
	10. Other non-current assets:
	Other non-current assets as of March 31, 2013 and 2014 consist of the following:
			Yen in millions
			March 31
			2013		2014
	Intangible assets *1		¥	63,989	¥	68,606
	Deferred tax assets			7,116		1,482
	Other *2			5,810		7,599
			¥	76,915	¥	77,687
	Notes:
	*1	“Intangible assets” information is described in Note 4 “Goodwill and other intangible assets”
	*2	“Other” primarily consists of Long-term prepaid expenses.

Shortterm_borrowings_and_longt

Short-term borrowings and long-term debt	12 Months Ended
	Mar. 31, 2014
Short-term borrowings and long-term debt	'
	11. Short-term borrowings and long-term debt:
	Short-term borrowings at March 31, 2013 and 2014 consist of the following:
		Yen in millions
		March 31
		2013			2014
	Loans, principally from banks with average interest at March 31, 2013 and 2014 of 0.21% and 0.31% per annum, respectively	¥	32,798		¥	22,600
		¥	32,798		¥	22,600
	At March 31, 2014, NIDEC had unused lines of credit amounting to ¥228,674 million with banks. Under these programs, NIDEC is authorized to obtain short-term financing at prevailing interest rates.
	Long-term debt at March 31, 2013 and 2014 are comprised of the following:
		Yen in millions
		March 31
		2013			2014
	Unsecured loans, representing obligations principally to banks and an insurance company
	Due 2013 to 2026 in 2013 with interest ranging from 0.00% to 6.40% per annum in 2013	¥	73,925			—
	Due 2014 to 2026 in 2014 with interest ranging from 0.00% to 6.80% per annum in 2014		—		¥	77,804
	Zero coupon convertible bonds due 2015		100,247			95,891
	Convertible at ¥5,313 for one common share
	Unsecured straight bonds due 2017		65,000			65,000
	Interest at 0.39% per annum in 2013 and 2014
	Unsecured straight bonds due 2019		15,000			15,000
	Interest at 0.60% per annum in 2013 and 2014
	Unsecured straight bonds due 2022		20,000			20,000
	Interest at 0.96% per annum in 2013 and 2014
	Unsecured straight bonds due 2016		—			50,000
	Interest at 0.21% per annum in 2014
	Unsecured straight bonds due 2014		100			100
	Issued by subsidiaries in 2011 which was newly consolidated in 2013
	Interest at 0.72% per annum in 2013 and 2014
	Capital lease obligations
	Due 2013 to 2019 in 2013, with interest from 0.00% to 8.27% per annum in 2013		5,627			—
	Due 2014 to 2019 in 2014, with interest from 0.00% to 15.74% per annum in 2014		—			4,861
			279,899			328,656
	Less—Bonds current portion due within one year		(100,247	)		(100	)
	Less—Long-term debt current portion due within one year		(31,841	)		(27,478	)
	Less—Capital lease obligation current portion due within one year		(1,540	)		(1,667	)
		¥	146,271		¥	299,411
	Note:
	Detail of Zero coupon convertible bonds, due 2015 is as follow;
		Yen in millions
		March 31
		2013			2014
	Principal amount	¥	100,000		¥	95,750
	Unamortized premium		247			141
	Total	¥	100,247		¥	95,891
	The euro yen denominated zero coupon convertible bonds with stock acquisition rights due 2015, which are listed at Singapore Stock Exchange, were issued on September 21, 2010, and are redeemable at 100% of principal amount on September 18, 2015 (maturity date). Concerning stock acquisition rights, the conversion price per share was ¥5,313 and the number of convertible shares is 18,021,833 as of March 31, 2014. The bonds are included in the calculation of diluted earnings per share as their impact is dilutive.
	The bonds were reclassified from Current portion of long-term debt to Long-term debt, since the unexercised early redemption right to redeem such bonds at 100% of its principal amount expired. Prior to the expiration of the early redemption right on September 20, 2013, holders of ¥4,250 million aggregate principal amount of such convertible bonds exercised their early redemption right.
	On April 1, 2014, the Company completed a two-for-one stock split. As a result, the conversion price of the Company’s Euro Yen Convertible Bonds with Stock Acquisition Rights due 2015 is adjusted from ¥10,626 to ¥5,313 and the number of convertible shares is changed from 9,010,916 to 18,021,833, pursuant to the Terms and Conditions of the Bonds set forth in the Offering Circular.
	NIDEC was not required to bifurcate any of the embedded features contained in the bonds for accounting purposes.
	The aggregate amounts of annual maturity of long-term debt during the next five years are as follows:
		Yen in millions
		Year ending
		March 31
	2015	¥	29,245
	2016		116,841
	2017		81,153
	2018		66,167
	2019		137
	2020 and thereafter	¥	35,113
	Standard agreements with certain banks in Japan include provisions that collateral (including sums on deposit with such banks) or guarantees will be furnished upon the banks’ request and that any collateral furnished, pursuant to such agreements or otherwise, will be applicable to all present or future indebtedness to such banks. There was no collateral furnished pursuant to the standard agreements with banks as of March 31, 2013 and 2014.

Other_current_liabilities

Other current liabilities	12 Months Ended
	Mar. 31, 2014
Other current liabilities	'
	12. Other current liabilities:
	Other current liabilities as of March 31, 2013 and 2014 consist of the following:
		Yen in millions
		March 31
		2013		2014
	Accounts payable for property, plant and equipment	¥	10,354	¥	9,857
	Advances received		6,437		7,152
	Income taxes payable		4,013		4,557
	Other		11,628		11,576
		¥	32,432	¥	33,142
	“Other” primarily consists of product warranty liabilities.

Pension_and_severance_plans

Pension and severance plans	12 Months Ended
	Mar. 31, 2014
Pension and severance plans	'
	13. Pension and severance plans:
	The Company and certain subsidiaries sponsor pension and retirement plans, which entitle employees, under most circumstances, to lump-sum indemnities or pension payments based on current rates of pay and length of service or the number of “points.” Under normal circumstances, the minimum payment prior to retirement age is an amount based on voluntary retirement. Employees receive additional benefits upon involuntary retirement, including retirement at the mandatory retirement age.
	For the year ended March 31, 2014, certain subsidiaries in Japan modified the terms of the defined benefit plan.
	According to the changes, gains and loss from prior service credit were recognized in consolidated financial statements.
	Information regarding NIDEC’s employees’ defined benefit plans is as follows:
	Japanese plans:
			Yen in millions
			March 31
			2013			2014
	Change in benefit obligation:
	Benefit obligation at beginning of year		¥	14,255		¥	14,079
	Service cost			910			927
	Interest cost			197			180
	Actuarial loss			163			196
	Acquisition and other			26			4,014
	Plan amendment			—			(143	)
	Benefits paid			(1,472	)		(1,851	)
				14,079			17,402
	Change in plan assets:
	Fair value of plan assets at beginning of year			7,096			7,827
	Actual return on plan assets			823			576
	Employer contribution			622			1,135
	Acquisition and other			—			2,856
	Benefits paid			(714	)		(963	)
	Fair value of plan assets at end of year			7,827			11,431
	Funded status		¥	(6,252	)	¥	(5,971	)
	Amounts included in the consolidated balance sheet are comprised of:
			Yen in millions
			March 31
			2013			2014
	Accrued pension and severance costs		¥	6,272		¥	6,045
	Other non-current assets			(20	)		(74	)
	Net amounts recognized		¥	6,252		¥	5,971
	Amounts included in accumulated other comprehensive income (loss) as pension liability adjustments are comprised of:
			Yen in millions
			March 31
			2013			2014
	Actuarial loss		¥	(1,741	)	¥	(1,562	)
	Prior service credit			1,407			1,393
	Pension liability adjustments, pre-tax		¥	(334	)	¥	(169	)
	The accumulated benefit obligations for all defined benefit pension plans were ¥13,873 million and ¥17,136 million for the years ended March 31, 2013 and 2014, respectively.
	The projected benefit obligation, accumulated benefit obligation and fair value of plan assets for which the accumulated benefit obligations exceed plan assets are as follows:
			Yen in millions
			March 31
			2013			2014
	Projected benefit obligations		¥	13,924		¥	12,805
	Accumulated benefit obligations			13,718			12,539
	Fair value of plan assets		¥	7,653		¥	6,725
	Weighted-average assumptions used to determine benefit obligations as of March 31, 2013 and 2014 are as follows:
			March 31
			2013			2014
	Discount rate			1.3	%		1.2	%
	Rate of compensation increase			2.2	%		4.2	%
	Weighted-average assumptions used to determine net pension and severance costs for the years ended March 31, 2012, 2013 and 2014 are as follows:
			For the year ended
			March 31
			2012			2013			2014
	Discount rate			1.6	%		1.6	%		1.3	%
	Expected return on plan assets			2.3	%		2.3	%		2.6	%
	Rate of compensation increase			2.2	%		2.3	%		2.2	%
			Yen in millions
			For the year  ended
			March 31
		2012			2013			2014
Components of net periodic (benefit) cost:
Service cost		¥	983		¥	910		¥	927
Interest cost			213			197			180
Expected return on plan assets			(134	)		(139	)		(164	)
Amortization of net actuarial loss			120			123			92
Amortization of prior service credit			(171	)		(146	)		(157	)
Losses from curtailments and settlements			296			—			—
Net periodic pension cost		¥	1,307		¥	945		¥	878
Prior service cost and actuarial gain and loss are amortized using the straight-line method over the average remaining service period of active employees. The estimated prior service credit and net actuarial loss for the defined benefit pension plans that will be amortized from accumulated other comprehensive income into benefits cost for the year ending March 31, 2015 are ¥157 million and ¥75 million, respectively.
Foreign plans:
		Yen in millions
		March 31
		2013			2014
Change in benefit obligation:
Benefit obligation at beginning of year		¥	6,119		¥	19,966
Service cost			549			553
Interest cost			625			741
Actuarial loss (gain)			992			(548	)
Acquisition and other			10,171			131
Foreign currency exchange rate changes			2,297			2,155
Benefits paid			(787	)		(1,032	)
			19,966			21,966
Change in plan assets:
Fair value of plan assets at beginning of year			563			7,014
Actual return on plan assets			505			957
Employer contribution			588			2,103
Acquisition and other			4,994			—
Foreign currency exchange rate changes			886			714
Benefits paid			(522	)		(675	)
Fair value of plan assets at end of year			7,014			10,113
Funded status		¥	(12,952	)	¥	(11,853	)
Amounts included in the consolidated balance sheet are comprised of:
		Yen in millions
		March 31
		2013			2014
Accrued pension and severance costs		¥	12,952		¥	11,853
Net amounts recognized		¥	12,952		¥	11,853
Amounts included in accumulated other comprehensive income (loss) as pension liability adjustments are comprised of:
		Yen in millions
		March 31
		2013			2014
Actuarial loss		¥	(952	)	¥	142
Pension liability adjustments, pre-tax		¥	(952	)	¥	142
The accumulated benefit obligations for all defined benefit pension plans were ¥19,708 million and ¥21,768 million for the years ended March 31, 2013 and 2014, respectively.
The projected benefit obligations, accumulated benefit obligations and fair value of plan assets for which the accumulated benefit obligations exceed plan assets are as follows:
		Yen in millions
		March 31
		2013			2014
Projected benefit obligations		¥	19,966		¥	21,498
Accumulated benefit obligations			19,708			21,300
Fair value of plan assets		¥	7,014		¥	9,464
Weighted-average assumptions used to determine benefit obligations as of March 31, 2013 and 2014 are as follows:
		March 31
		2013			2014
Discount rate			4.4	%		4.4	%
Rate of compensation increase			3	%		3	%
Weighted-average assumptions used to determine net pension and severance costs for the years ended March 31, 2012, 2013 and 2014 are as follows:
		For the year ended
		March 31
		2012			2013			2014
Discount rate			5.7	%		4.7	%		4.4	%
Expected return on plan assets			4.4	%		7.5	%		7.5	%
Rate of compensation increase			2.9	%		3	%		3	%
		Yen in millions
		For the year  ended
		March 31
		2012			2013			2014
Components of net periodic (benefit) cost:
Service cost		¥	441		¥	549		¥	553
Interest cost			230			625			741
Expected return on plan assets			(48	)		(445	)		(443	)
Amortization of net actuarial loss (gain)			(2	)		6			27
Net periodic pension cost		¥	621		¥	735		¥	878
Actuarial gain and losses are amortized using the straight-line method over the average remaining service period of active employees. The estimated net actuarial losses for the defined benefit pension plans that will be amortized from accumulated other comprehensive income into benefits cost for the year ending March 31, 2015 is ¥12 million.
Japanese plans and foreign plans:
NIDEC’s policy and objective for plan asset management is to generate a stable return on the investment over the long term, which enables NIDEC’s pension funds to meet future benefit payment requirements under risks which NIDEC considers permissible. NIDEC formulates “basic” portfolio that suits the above-mentioned policy, and ensures that plan assets are allocated under this “basic” portfolio. NIDEC evaluates its actual return and revises the “basic” portfolio, if necessary.
NIDEC’s portfolio for plans consists of three major components: approximately 2% is invested in equity securities, approximately 4% is invested in debt securities, and approximately 94% is invested in other investment vehicles, primarily consisting of investments in pooled funds and life insurance company general accounts.
The equity securities are selected from stocks that are listed on the securities exchanges. The debt securities are selected from Japanese and foreign government bonds, public debt instruments, and corporate bonds. Pooled funds included in other assets invest in equity and debt securities in mixture selected from same as above two categories. As for investments in life insurance company general accounts, the contracts with the insurance companies include a guaranteed interest rate and return of capital.
The three levels of input used to measure fair value are more fully described in Note 19. The fair values of NIDEC’s pension plan assets at March 31, 2013 and 2014, by asset category, are as follows:
		Yen in millions
		Fair Value  at			Fair Value Measurements
		March 31, 2013			Using Inputs Considered as
					Level 1			Level 2			Level 3
Equity securities:
Japanese companies		¥	302		¥	302		¥	—		¥	—
Foreign companies			302			302			—			—
Debt securities:
Pooled funds *1			593			—			593			—
Other assets:
Cash and cash equivalents			1,103			1,103			—			—
Life insurance company general accounts			3,040			—			3,040			—
Pooled funds *2			7,431			—			7,431			—
Others			2,070			—			—			2,070
Total		¥	14,841		¥	1,707		¥	11,064		¥	2,070
*1	These funds invest in approximately 86% Japanese bonds, 14% foreign bonds.
*2	These funds primarily invest in listed equity securities consisting of approximately 12% Japanese companies and 60% foreign companies, and debt security consisting of approximately 9% Japanese bonds and 16% foreign bonds.
		Yen in millions
		Fair Value  at			Fair Value Measurements
		March 31, 2014			Using Inputs Considered as
					Level 1			Level 2			Level 3
Equity securities:
Japanese companies		¥	281		¥	281		¥	—		¥	—
Foreign companies			233			233			—			—
Debt securities:
Pooled funds *1			757			—			757			—
Other assets:
Cash and cash equivalents			1,793			1,793			—			—
Life insurance company general accounts			4,833			—			4,833			—
Pooled funds *2			11,183			—			11,183			—
Others			2,464			—			2,464			—
Total		¥	21,544		¥	2,307		¥	19,237		¥	—
*1	These funds invest in approximately 68% Japanese bonds, 32% foreign bonds.
*2	These funds primarily invest in listed equity securities consisting of approximately 7% Japanese companies and 31% foreign companies, and debt security consisting of approximately 6% Japanese bonds and 37% foreign bonds.
Level 1 assets are comprised primarily of cash and cash equivalents and equity securities, which are valued using an unadjusted quoted market price in active markets with sufficient volume and frequency of transactions. Level 2 assets are comprised primarily of pooled funds that invest in equity and debt securities, and investments in life insurance company general accounts. Pooled funds are valued at their net asset values that are calculated by the sponsor of the fund and have daily liquidity. The net asset value is based on the fair value of the underlying assets owned by the fund, minus its liabilities then divided by the number of units outstanding. Investments in life insurance company general accounts are valued at conversion value.
The table below sets forth a summary of changes in the fair value of plan assets categorized as Level 3 for the years ended March 31, 2013 and 2014.
Others		Yen in millions
		March 31			March 31
		2013			2014
Balance at beginning of year		¥	—		¥	2,070
Acquisition *1			1,159			—
Purchases			582			—
Actual return on plan assets and other			329			394
Transfers out of level 3 *2			—			(2,464	)
Balance at end of year		¥	2,070		¥	—
*1	As a result of the Acquisition of Minster, NIDEC acquired the plan assets categorized as Level 3.
*2	All the level 3 assets were transferred into level 2 because we got the ability to redeem the level 3 assets at net asset value at the measurement date.
Others consist primarily of interests in common/collective trusts. The investments employ a funds of funds strategy in various hedge funds with multiple strategies. These investments are valued using the net asset values as provided by the funds.
NIDEC expects to contribute approximately ¥1,477 million to its defined benefit plans for the year ending March 31, 2015.
The future benefit payments for defined benefit plans are expected as follows:
		Yen in millions
		Japanese			Foreign
		plans			plans
2015		¥	811		¥	1,030
2016			932			1,043
2017			886			942
2018			892			1,122
2019			1,153			1,121
Years 2020-2024		¥	5,667		¥	5,709
Certain subsidiaries have a number of multiemployer plans. Total amounts of cost recognized for certain subsidiaries’ contributions to the plans were ¥252 million, ¥182 million and ¥169 million for the years ended March 31, 2012, 2013 and 2014, respectively. NIDEC expects to contribute approximately ¥156 million for the year ending March 31, 2015.
Certain subsidiaries have a number of defined contribution plans. Total amounts of cost recognized for certain subsidiaries’ contribution to the plans were ¥1,533 million, ¥1,999 million and ¥2,617 million for the years ended March 31, 2012, 2013 and 2014, respectively. NIDEC expects to contribute approximately ¥2,839 million for the year ending March 31, 2015.

Other_longterm_liabilities

Other long-term liabilities	12 Months Ended
	Mar. 31, 2014
Other long-term liabilities	'
	14. Other long-term liabilities:
	Other long-term liabilities as of March 31, 2013 and 2014 consist of the following:
			Yen in millions
			March 31
			2013		2014
	Deferred tax liabilities		¥	14,715	¥	17,138
	Unrecognized tax benefits, accrued interest and penalty*			2,173		2,321
	Other			4,329		5,785
			¥	21,217	¥	25,244
	* Note:	“Unrecognized tax benefits, accrued interest and penalty” information is described in Note 16 “Income taxes”

Equity

Equity	12 Months Ended
	Mar. 31, 2014
Equity	'
	15. Equity:
	The Japanese Company Law (the “Company Law”) provides that an amount equal to 10% of cash dividends from retained earnings by the Company and its Japanese subsidiaries must be appropriated as a legal reserve. No further appropriations are required when the sum of the legal reserves reaches 25% of stated capital. These reserves currently exceed 25% of stated capital and are available for dividends under the Company Law subject to approval at the shareholders’ meeting. Certain foreign subsidiaries are also required to appropriate their earnings to legal reserves under the laws of the respective countries.
	The amount of statutory retained earnings of the Company available for dividend payments to shareholders was ¥69,109 million and ¥91,137 million for the years ended March 31, 2013 and 2014, respectively. In accordance with customary practice in Japan, the appropriations are not accrued in the financial statements for the period to which they relate, but are recorded in the subsequent accounting period. Retained earnings for the year ended March 31, 2014 includes amounts representing final cash dividends of ¥7,585 million, ¥27.5 per share.
	Repurchased treasury stock is not entitled to a dividend under the Company Law. NIDEC resolved to repurchase its own shares at several meetings of its Board of Directors during the years ended March 31, 2013 and 2014. In accordance with the resolution, NIDEC repurchased 10,156,400 shares of treasury stock for the aggregate cost of ¥31,209 million and 1,000,000 shares of treasury stock for the aggregate cost of ¥2,696 million during years ended March 31, 2013 and 2014. NIDEC owned 20,311,044 shares, or ¥56,109 million and 14,343,952 shares, or ¥40,527 million of treasury stock repurchased for the years ended March 31, 2013 and 2014, which were restricted regarding the payment of cash dividend.
	On October 1, 2012, NIDEC made the Nidec Sankyo Corporation (“NSNK”) a wholly owned subsidiary through a share exchange transaction. NIDEC allocated 6,350,630 shares of its common stock held in treasury to holders of NSNK stock in connection with the share exchange transaction. As a result of the share exchange transaction, NIDEC’s equity interests in NSNK increased from 77.1% to 100%.
	On October 1, 2013, NIDEC made the Nidec Copal Corporation (“NCPL”) a wholly owned subsidiary through a share exchange transaction. NIDEC allocated 4,856,764 shares of its common stock held in treasury to holders of NCPL stock in connection with the share exchange transaction. As a result of the share exchange transaction, NIDEC’s equity interest in NCPL increased from 66.5% to 100.0%.
	On October 1, 2013, NIDEC made the Nidec Tosok Corporation (“NTSC”) a wholly owned subsidiary through a share exchange transaction. NIDEC allocated 2,624,000 shares of its common stock held in treasury to holders of NTSC stock in connection with the share exchange transaction. As a result of the share exchange transaction, NIDEC’s equity interest in NTSC increased from 72.3% to 100.0%.
	NIDEC implemented a two-for-one stock split on NIDEC’s common stock as of March 31, 2014.Therefore, NIDEC adjusted shares of common stock and those of treasury stock under the assumption that the stock split had been implemented on March 31, 2012, retrospectively.
	Retained earnings relating to equity in undistributed earnings reflect ¥190 million, ¥152 million and ¥168 million of accumulated deficit of the companies accounted for by the equity method for the years ended March 31, 2012, 2013 and 2014.
	The changes in accumulated other comprehensive income (loss) by component are as follows:
			Yen in Millions
			Foreign			Unrealized			Unrealized			Pension			Total
			currency			gains			gains			liability
			translation			(losses)			(losses)			adjustments
			adjustments			from			from
						securities			derivative
									instruments
	For the year ended March 31, 2014:
	Balance at March 31, 2013			12,636			1,187			242			(1,112	)		12,953
	Other comprehensive income (loss) before reclassifications			41,903			3,145			(244	)		754			45,558
	Amounts reclassified from accumulated other comprehensive income (loss)			—			(147	)		(22	)		34			(135	)
	Net change during the current period other comprehensive income (loss)			41,903			2,998			(266	)		788			45,423
	Balance at March 31, 2014			54,539			4,185			(24	)		(324	)		58,376
	Reclassification out of accumulated other comprehensive income (loss) are as follows:
			Yen in Millions
			Amount			Affected line items
			Reclassified			in consolidated statement of income
			from
			Accumulated
			other
			comprehensive
			income (loss) *1
	For the year ended March 31, 2014:
	Unrealized gains (losses) from securities			(230	)	Gain from marketable securities, net
				83		Income taxes
				(147	)	Consolidated net income
				—		Net income attributable to noncontrolling interests
				(147	)	Net income attributable to Nidec Corporation
	Unrealized gains (losses) from derivative instruments			(37	)	Cost of products sold, Interest expense.
				15		Income taxes
				(22	)	Consolidated net income
				—		Net income attributable to noncontrolling interests
				(22	)	Net income attributable to Nidec Corporation
	Pension liability adjustments			(38	)	*2
				22		Income taxes
				(16	)	Consolidated net income
				50		Net income attributable to noncontrolling interests
				34		Net income attributable to Nidec Corporation
	Total amount reclassified, net of tax and noncontrolling interests			(135	)
	*1	Amounts in parentheses indicate gains in consolidated statement of income.
	*2	This accumulated other comprehensive income (loss) component is included in the computation of net periodic pension cost.
	Tax effects allocated to each component of other comprehensive income (loss) and reclassification adjustments, including amounts attributable to noncontrolling interests for the years ended March 31, 2012, 2013 and 2014 are as follows:
			Yen in millions
			Pre-tax			Tax  benefit/			Net-of-tax
			amount			(expense)			amount
	For the year ended March 31, 2012:
	Foreign currency translation adjustments:
	Foreign currency translation adjustments arising during period		¥	(2,665	)	¥	—		¥	(2,665	)
	Reclassification adjustments for gains and losses realized in net income			105			—			105
	Unrealized gains (losses) from securities:
	Unrealized holding losses arising during period			(358	)		129			(229	)
	Reclassification adjustments for gains and losses realized in net income			253			(31	)		222
	Unrealized gains (losses) from derivative instruments qualifying for cash flow hedges:
Unrealized losses arising during period			(541	)		216			(325	)
Reclassification adjustments for gains and losses realized in net income			291			(112	)		179
Pension liability adjustment:
Actuarial losses arising during period			(831	)		114			(717	)
Prior service cost arising during period			(10	)		4			(6	)
Reclassification adjustments for actuarial gains and losses realized in net income			891			(340	)		551
Reclassification adjustments for prior service credit and cost realized in net income			463			(198	)		265
Other comprehensive income (loss)		¥	(2,402	)	¥	(218	)	¥	(2,620	)
For the year ended March 31, 2013:
Foreign currency translation adjustments:
Foreign currency translation adjustments arising during period		¥	62,024		¥	—		¥	62,024
Reclassification adjustments for gains and losses realized in net income			134			—			134
Unrealized gains (losses) from securities:
Unrealized holding gains arising during period			156			(56	)		100
Reclassification adjustments for gains and losses realized in net income			88			(37	)		51
Unrealized gains (losses) from derivative instruments qualifying for cash flow hedges:
Unrealized gains arising during period			93			(30	)		63
Reclassification adjustments for gains and losses realized in net income			196			(90	)		106
Pension liability adjustment:
Actuarial losses arising during period			(328	)		(93	)		(421	)
Prior service cost arising during period			—			—			—
Reclassification adjustments for actuarial gains and losses realized in net income			130			(45	)		85
Reclassification adjustments for prior service credit and cost realized in net income			(152	)		55			(97	)
Other comprehensive income (loss)		¥	62,341		¥	(296	)	¥	62,045
For the year ended March 31, 2014:
Foreign currency translation adjustments:
Foreign currency translation adjustments arising during period		¥	43,429		¥	—		¥	43,429
Reclassification adjustments for gains and losses realized in net income			—			—			—
Unrealized gains (losses) from securities:
Unrealized holding gains arising during period			4,567			(1,440	)		3,127
Reclassification adjustments for gains and losses realized in net income			(230	)		83			(147	)
Unrealized gains (losses) from derivative instruments qualifying for cash flow hedges:
Unrealized losses arising during period			(397	)		153			(244	)
Reclassification adjustments for gains and losses realized in net income			(37	)		15			(22	)
Pension liability adjustment:
Actuarial gains arising during period			1,071			(378	)		693
Prior service cost arising during period			74			(14	)		60
Reclassification adjustments for actuarial gains and losses realized in net income			119			(35	)		84
Reclassification adjustments for prior service credit and cost realized in net income			(157	)		57			(100	)
Other comprehensive income (loss)		¥	48,439		¥	(1,559	)	¥	46,880

Income_taxes

Income taxes	12 Months Ended
	Mar. 31, 2014
Income taxes	'
	16. Income taxes:
	The components of income from continuing operations before income tax comprise the following:
		Yen in millions
		For the year ended
		March 31
		2012			2013			2014
	Income (loss) from continuing operations before income taxes:
	The Company and domestic subsidiaries	¥	46,181		¥	(7,473	)	¥	25,463
	Foreign subsidiaries		24,675			20,871			59,201
		¥	70,856		¥	13,398		¥	84,664
	The provision for income taxes consists of the following:
		Yen in millions
		For the year ended
		March 31
		2012			2013			2014
	Current income tax expense/(benefit):
	The Company and domestic subsidiaries	¥	(4,462	)	¥	9,200		¥	1,872
	Foreign subsidiaries		6,694			5,713			10,139
	Total current		2,232			14,913			12,011
	Deferred income tax expense (benefit):
	The Company and domestic subsidiaries		16,289			(5,504	)		12,649
	Foreign subsidiaries		280			(2,847	)		1,069
	Total deferred		16,569			(8,351	)		13,718
	Total provision	¥	18,801		¥	6,562		¥	25,729
	NIDEC is subject to a number of different income taxes, which, in the aggregate, indicate a statutory rate in Japan of approximately 41.0% in 2012 and approximately 38.0% in 2013 and 2014. Reconciliation of the differences between the statutory tax rate and the effective income tax rate is as follows:
		For the year ended
		March 31
		2012			2013			2014
	Statutory tax rate		41	%		38	%		38	%
	Increase (reduction) in taxes resulting from:
	Tax benefit in foreign subsidiaries		(16.1	)		(43.6	)		(14.6	)
	Tax on undistributed earnings		5.1			8.9			2.2
	Valuation allowance		4.1			33.7			(2.3	)
	Liabilities for unrecognized tax benefits		(10.5	)		2.3			(0.1	)
	Reversal of deferred tax assets related to foreign tax credit		—			—			5.3
	Changes in Japanese income tax rates		1.4			—			0.3
	Other		1.5			9.7			1.6
	Effective income tax rate		26.5	%		49	%		30.4	%
	The effective income tax rate decreased 18.6 percentage points from 49.0% for the year ended March 31, 2013 to 30.4% for the year ended March 31, 2014. This was mainly due to provision for valuation allowance relating to the tax losses at some of our subsidiaries carried forward for the year ended March 31, 2013 which was more than offset by reversal of valuation allowance for the year ended March 31, 2014 at some of our other subsidiaries due to recovery in their business performance.
	Impact of tax benefit in foreign subsidiaries decreased 29.0 percentage points from minus 43.6% for the year ended March 31, 2013 to minus 14.6% for the year ended March 31, 2014. This was because the income before income taxes increased for the year ended March 31, 2014 compared to the year ended March 31, 2013, especially in domestic subsidiaries.
	Tax benefit in foreign subsidiaries primarily relates to income sourced from foreign subsidiaries mainly in Thailand and the Philippines.
	In Thailand, NIDEC received privileges under the promotional certificates issued in March and August 2010. Under these privileges, NIDEC received an exemption from corporate income tax for a period of eight years from the date of commencement of certain revenue-generating activities identified by the promotional certificate.
	In the Philippines, NIDEC received certain tax incentives in September 2011, which included an income tax holiday for four years.
	The aggregate amounts and per share effects of tax holidays are as follows:
		Yen in millions
		For the year ended
		March 31
		2012			2013			2014
	Aggregate amounts of tax holidays	¥	4,023		¥	2,968		¥	4,362
		Yen
	Per share—basic	¥	14.63		¥	11.02		¥	16.03
	—diluted	¥	13.69		¥	10.3		¥	15.02
	The significant components of deferred tax assets and liabilities are as follows:
		Yen in millions
		March 31
		2013			2014
	Deferred tax assets:
	Inventories	¥	3,142		¥	2,818
	Marketable securities		1,102			—
	Property, plant and equipment		—			5,019
	Accrued bonus		2,242			2,330
	Accrued enterprise tax		—			221
	Pension and severance plans		4,526			4,464
Operating loss carryforwards for tax purposes		13,646			12,811
Foreign tax credit		5,402			—
Accrued vacation		1,135			1,090
Accrued expenses		3,636			1,421
Other		2,613			2,666
Gross deferred tax assets		37,444			32,840
Less—Valuation allowance		(14,492	)		(14,561	)
Net deferred tax assets		22,952			18,279
Deferred tax liabilities:
Refund of enterprise taxes		(285	)		—
Basis difference of acquired assets		(4,495	)		(458	)
Property, plant and equipment		(1,058	)		—
Undistributed earnings not permanently reinvested		(7,856	)		(9,311	)
Marketable securities		—			(321	)
Intangible assets		(4,816	)		(9,813	)
Other		(1,083	)		(5,181	)
Gross deferred tax liabilities		(19,593	)		(25,084	)
Net deferred tax assets (liabilities)	¥	3,359		¥	(6,805	)
Operating loss carryforwards for tax purposes on March 31, 2014 amounted to approximately ¥35,843 million and are available as an offset against future taxable income of such subsidiaries.
With the exception of ¥6,245 million with no expiration period, total available operating loss carryforwards will expire at various dates primarily up to 9 years. Operating loss carryforwards for tax purposes occurred mainly in Japan and will become expired primarily up to 2023.
The valuation allowance mainly relates to deferred tax assets of consolidated subsidiaries with operating loss carryforwards for tax purposes that are not expected to be realized. The net changes in the total valuation allowance for deferred tax assets for the years ended March 31, 2012, 2013 and 2014 consist of the following:
	Yen in millions
	March 31
	2012			2013			2014
Valuation allowance at beginning of year	¥	(6,235	)	¥	(9,786	)	¥	(14,492	)
Additions		(3,490	)		(7,660	)		(4,231	)
Deductions		1,581			2,994			4,183
Impact on newly acquired companies		(1,642	)		(40	)		(21	)
Valuation allowance at end of year	¥	(9,786	)	¥	(14,492	)	¥	(14,561	)
Net deferred tax assets are included in the consolidated balance sheets as follows:
	Yen in millions
	March 31
	2013			2014
Deferred tax assets:
Other current assets	¥	12,787		¥	10,434
Other non-current assets		7,116			1,482
Deferred tax liabilities:
Other current liabilities		(1,829	)		(1,583	)
Other long-term liabilities		(14,715	)		(17,138	)
Net deferred tax assets	¥	3,359		¥	(6,805	)
Management of NIDEC intends to reinvest certain undistributed earnings of foreign subsidiaries for an indefinite period of time. As a result, no deferred tax liability has been recorded on undistributed earnings of these subsidiaries, which are not expected to be remitted in the foreseeable future, aggregating ¥157,931 million as of March 31, 2014. NIDEC estimates an additional deferred tax liability of ¥11,558 million would be required at such time if the full amount of these accumulated earnings were expected to be remitted.
A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows:
	Yen in millions
	For the year ended
	March 31,
	2012			2013			2014
Balance at April 1	¥	9,199		¥	1,766		¥	2,361
Additions for tax positions of the current year		1,766			44			357
Additions for tax positions of prior years		—			551			—
Reduction for tax positions of prior years		—			—			(486	)
Settlements		(9,199	)		—			—
Balance at March 31	¥	1,766		¥	2,361		¥	2,232
Total amount of unrecognized tax benefits that would reduce the effective tax rate, if recognized, is ¥2,232 million.
Although NIDEC believes its estimates and assumptions of unrecognized tax benefits are reasonable, uncertainty regarding the final determination of tax audit settlements and any related litigation could affect the effective tax rate in the future periods. A significant change to the unrecognized tax benefits might occur within the next twelve months. NIDEC does not expect that such change will have a significant impact on consolidated results of operations and financial position.
NIDEC recognizes interest and penalties related to unrecognized tax benefits as a component of other, net in the consolidated statements of income. The interest and penalties for the fiscal years ended March 31, 2012, 2013 and 2014, respectively, had no material impact on its consolidated results of operations. The total gross accrued interest and penalty were ¥192 million and ¥89 million at March 31, 2013 and 2014, respectively.
NIDEC remains subject to income tax examination for the tax returns related to the years beginning on and after January 1, 2007, with various tax jurisdictions including Japan.

Reconciliation_of_the_differen

Reconciliation of the differences between basic and diluted earnings per share	12 Months Ended
	Mar. 31, 2014
Reconciliation of the differences between basic and diluted earnings per share	'
	17. Reconciliation of the differences between basic and diluted earnings per share:
	The tables below set forth a reconciliation of the differences between basic and diluted income attributable to Nidec Corporation per share for the years ended March 31, 2012, 2013 and 2014.
		Yen in			Thousands of		Yen
		millions			shares
		Net income			Weighted-		Net income
		(loss)			average		(loss)
		attributable to			shares		attributable to
		Nidec					Nidec
		Corporation					Corporation
							per share
	For the year ended March 31, 2012:
	Basic net income attributable to Nidec Corporation per share:
	Income from continuing operations attributable to Nidec Corporation	¥	46,242			274,981	¥	168.16
	Loss on discontinued operations attributable to Nidec Corporation		(5,511	)		274,981		(20.04	)
	Net income attributable to Nidec Corporation		40,731			274,981		148.12
	Effect of dilutive securities:
	Zero coupon convertible bonds		(55	)		18,821
	Diluted net income attributable to Nidec Corporation per share:
	Income from continuing operations attributable to Nidec Corporation		46,187			293,802		157.2
	Loss on discontinued operations attributable to Nidec Corporation		(5,511	)		293,802		(18.75	)
	Net income attributable to Nidec Corporation	¥	40,676			293,802	¥	138.45
	For the year ended March 31, 2013:
	Basic net income attributable to Nidec Corporation per share:
	Net income attributable to Nidec Corporation	¥	7,986			269,429	¥	29.64
	Effect of dilutive securities:
	Zero coupon convertible bonds		(61	)		18,821
	Diluted net income attributable to Nidec Corporation per share:
	Net income attributable to Nidec Corporation	¥	7,925			288,250	¥	27.49
		Yen in			Thousands of		Yen
		millions			shares
		Net income			Weighted-		Net income
		(loss)			average		(loss)
		attributable to			shares		attributable to
		Nidec					Nidec
		Corporation					Corporation
							per share
	For the year ended March 31, 2014:
	Basic net income attributable to Nidec Corporation per share:
	Net income attributable to Nidec Corporation	¥	56,404			272,078	¥	207.31
	Effect of dilutive securities:
	Zero coupon convertible bonds		(64	)		18,400
	Diluted net income attributable to Nidec Corporation per share:
	Net income attributable to Nidec Corporation	¥	56,340			290,478	¥	193.96
	NIDEC implemented a two-for-one stock split on our common stock effective April 1, 2014. Therefore, NIDEC adjusted the earnings per share have been accordingly adjusted to reflect the effect of the stock split.

Derivatives

Derivatives	12 Months Ended
	Mar. 31, 2014
Derivatives	'
	18. Derivatives:
	NIDEC manages the exposures to fluctuations in foreign exchange rate, interest rate, and commodity prices through the use of derivative financial instruments which include foreign exchange forward contracts, currency option contracts, interest rate swap agreement and commodity future contracts. NIDEC does not hold derivative financial instruments for trading purpose. NIDEC is exposed to credit risk in the event of non-performance by counterparties to the derivative contracts, but such risk is considered and mitigated by the high credit rating of the counterparties.
	Cash flow hedges
	NIDEC uses foreign exchange forward contracts, interest rate swap agreements and commodity future contracts designated as cash flow hedges to protect against a portion of foreign exchange rate risks, interest rate risks and commodity prices risks inherent in its forecasted transactions related to purchase commitments.
	Derivatives not designated as hedges
	NIDEC is unable or has elected not to apply hedge accounting to some of these derivatives from time to time. The changes in the fair value of these contracts are recorded in ‘Other income (expense)’.
	The contractual amounts outstanding of derivative instruments
	Derivatives designated as hedging instruments are as follows:
		Yen in millions
		March 31, 2013				March 31, 2014
	Foreign exchange forward contracts	¥	7,403			¥	9,736
	Interest rate swap agreements		32,205				20,587
	Commodity futures		3,739				4,610
	Derivatives not designated as hedging instruments are as follows:
		Yen in millions
		March 31, 2013				March 31, 2014
	Foreign exchange forward contracts	¥	149			¥	1,800
	Currency option contracts		231				53
	Fair values of derivative instruments
	Derivatives designated as cash flow hedge are as follows:
				Asset Derivatives
		Balance sheet location		Yen in millions
				March 31,				March 31,
				2013				2014
	Foreign exchange forward contracts	Other current assets		¥	659			¥	271
				Liability Derivatives
		Balance sheet location		Yen in millions
				March 31,				March 31,
				2013				2014
	Foreign exchange forward contracts	Other current liabilities		¥	22			¥	1
	Interest rate swap agreements	Other current liabilities			20				31
	Commodity futures	Other current liabilities			181				239
	Derivatives not designated as hedging instruments are as follows:
				Asset Derivatives
		Balance sheet location		Yen in millions
				March 31,				March 31,
				2013				2014
	Foreign exchange forward contracts	Other current assets		¥	16			¥	4
	Currency option contracts	Other current assets			10				7
	The effect of derivative instruments on the consolidated statements of income for the year ended March 31
	Derivatives designated as cash flow hedge are as follows:
	Gains (losses) recognized in accumulated other comprehensive income
		Yen in millions
		For the year ended March 31
		2012				2013				2014
	Foreign exchange forward contracts	¥	(68	)		¥	277			¥	(229	)
	Interest rate swap agreements		—				(6	)			(5	)
	Commodity futures		(78	)			(102	)			(32	)
	Gains (losses) reclassified from accumulated other comprehensive income into income (effective portion)
		Statement of income location		Yen in millions
				For the year ended March 31
				2012				2013				2014
	Foreign exchange forward contracts	Cost of sales		¥	17			¥	81			¥	241
	Interest rate swap agreements	Interest expense			—				(4	)			(7	)
	Commodity futures	Cost of sales			(196	)			(183	)			(212	)
	The amount of hedge ineffectiveness and net gains (losses) excluded from the assessment of hedge effectiveness was not material for the year ended March 31, 2014.
	A net loss of ¥27 million in accumulated other comprehensive income at March 31, 2014 is expected to be reclassified into earnings within the next 12 months.
	As of March 31, 2014, the maximum length of time over which NIDEC hedged its exposure to variability in future cash flows for forecasted transactions was approximately 23 months.
	Derivatives not designated as hedging instruments are as follows:
	Gains (losses) recognized in income
		Statement of income location		Yen in millions
				For the year ended March 31
				2012				2013				2014
Foreign exchange forward contracts	Foreign exchange gain (loss), net		¥	—			¥	22			¥	23
Currency option contracts	Foreign exchange gain (loss), net			—				40				18
Interest rate currency swap agreements	Other, net			2				—				—

Fair_Value

Fair Value	12 Months Ended
	Mar. 31, 2014
Fair Value	'
	19. Fair Value:
	Under Statement of ASC 820, “Fair Value Measurements and Disclosures”, fair value is defined as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. ASC 820 also establishes a hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the most observable inputs be used when available. Observable inputs are inputs that reflect the assumptions market participants would use in valuing the asset or liability developed based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect NIDEC’s assumptions about the factors market participants would use in valuing the asset or liability developed based upon the best information available in the circumstances. The hierarchy is broken down into three levels.
	Level 1 inputs are quoted prices in active markets for identical assets or liabilities.
	Level 2 inputs include 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 for the asset or liability, and inputs that are derived principally from or corroborated by observable market data by correlation or other means.
	Level 3 inputs are unobservable inputs for the asset or liability.
	Categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement.
	Assets and Liabilities that are measured at Fair Value on a Recurring Basis:
	The following table provides information by level for assets and liabilities that are measured at fair value, as defined by ASC 820, on a recurring basis.
		Yen in millions
		Fair Value  at			Fair Value Measurements
		March 31, 2013			Using Inputs Considered as
					Level 1			Level 2			Level 3
	Assets:
	Marketable securities	¥	14,060		¥	13,649		¥	411			—
	Derivatives		685			—			685			—
	Total assets:	¥	14,745		¥	13,649		¥	1,096			—
	Liabilities:
	Derivatives	¥	223		¥	181		¥	42			—
		Yen in millions
		Fair Value  at			Fair Value Measurements
		March 31, 2014			Using Inputs Considered as
					Level 1			Level 2			Level 3
	Assets:
	Marketable securities	¥	14,383		¥	14,383			—			—
	Derivatives		282			—			282			—
	Total assets:	¥	14,665		¥	14,383		¥	282			—
	Liabilities:
	Derivatives	¥	271		¥	239		¥	32			—
	Level 1 securities and derivatives including commodity futures are valued using an unadjusted quoted market price in active markets with sufficient volume and frequency of transactions.
	Level 2 securities are valued using non-active market prices for identical assets.
	Level 2 derivatives including foreign exchange contracts are valued using quotes obtained from counterparties or third parties, which are periodically validated by pricing models using observable market inputs, such as foreign currency exchange rates, and interest rates.
	Fair value of financial instruments:
	The carrying amount and estimated fair values of NIDEC’s financial instruments, excluding those disclosed elsewhere, are summarized as follows:
		Yen in millions						Yen in millions
		March 31, 2013						March 31, 2014
		Carrying			Estimated			Carrying			Estimated
		amount			fair value			amount			Fair value
	Asset (Liability):
	Cash and cash equivalents	¥	193,420		¥	193,420		¥	247,740		¥	247,740
	Short-term investments		1,552			1,552			2,344			2,344
	Long-term investments		—			—			83			82
	Short-term loan receivable		132			132			157			157
	Long-term loan receivable		89			91			48			50
	Short-term borrowings		(32,798	)		(32,798	)		(22,600	)		(22,600	)
	Long-term debt including the current portion and excluding capital lease obligation and bonds		(73,925	)		(73,907	)		(77,804	)		(77,486	)
	Bonds including the current portion	¥	(200,347	)	¥	(200,850	)	¥	(245,991	)	¥	(271,853	)
	The following are explanatory notes relating to the financial instruments.
	Cash and cash equivalents, short-term investments, short-term loans receivable and short-term borrowings: In the normal course of business, substantially all cash and cash equivalents, short-term investments (time deposits), short-term loans receivable and short-term borrowings are highly liquid and are carried at amounts that approximate fair value.
	Long-term investments: NIDEC’s long-term investments are time deposits which are due over one year from the year ended March 31, 2014 to original maturity and are classified as Level 2 instruments. The fair value of long-term investments was estimated by discounting expected future cash flows.
	Long-term loan receivable: NIDEC’s long-term loan receivable instruments are classified as Level 2 instruments. The fair value of long-term loans was estimated by discounting expected future cash flows.
	Long-term debt: NIDEC’s long-term debt instruments are classified as Level 2 instruments. The fair value of long-term bank loans (including the current portion and excluding the capital lease obligation and bonds) was estimated based on the discounted amounts of future cash flows using NIDEC’s current incremental borrowing rates for similar liabilities.
	Bonds: NIDEC’s bonds instruments are classified as Level 2 instruments. The fair value of bonds issued by NIDEC was estimated based on their market price that are not active other than quoted prices.
	Carrying amounts of “Trade notes and accounts receivable” and “Trade notes and accounts payable” approximate fair value because of the short maturity of these instruments. The table described above excludes these financial instruments.

Related_party_transactions

Related party transactions	12 Months Ended
	Mar. 31, 2014
Related party transactions	'
	20. Related party transactions:
	As of March 31, 2014, the Chief Executive Officer (“CEO”) of the Company, a business entity indirectly owned by the CEO (“the business entity”), and the CEO’s immediate family member held 9.1%, 4.0% and 1.9% of the outstanding shares of the Company, respectively.
	In October 2012, the Company entered into a share exchange transaction with NSNK to make NSNK a wholly owned subsidiary of the Company. The Company allocated 6,350,630 shares of the Company’s common stock held in treasury into shareholders of NSNK except for the Company. The CEO was allocated 306,272 shares of the Company’s common stock held in treasury in exchange for shares of NSNK which the CEO had owned. This related party transaction with the CEO was at arm’s-length. This related party transaction did not have a material impact on NIDEC’s consolidated financial position, results of operations and liquidity.
	In October 2013, the Company entered into a share exchange transaction with NCPL to make NCPL a wholly owned subsidiary of the Company. The Company allocated 4,856,764 shares of the Company’s common stock held in treasury into shareholders of NCPL except for the Company. The CEO was allocated 589,992 shares of the Company’s common stock held in treasury in exchange for shares of NCPL which the CEO had owned. This related party transaction with the CEO was at arm’s-length. This related party transaction did not have a material impact on NIDEC’s consolidated financial position, results of operations and liquidity.
	In October 2013, the Company entered into a share exchange transaction with NTSC to make NTSC a wholly owned subsidiary of the Company. The Company allocated 2,624,000 shares of the Company’s common stock held in treasury into shareholders of NTSC except for the Company. The CEO and the business entity were allocated 322,400 shares and 49,600 shares of the Company’s common stock, respectively, held in treasury in exchange for shares of NTSC which the CEO and the business entity had owned. These related party transactions with the CEO and the business entity was at arm’s-length. These related party transactions did not have a material impact on NIDEC’s consolidated financial position, results of operations and liquidity.

Lease_commitments

Lease commitments	12 Months Ended
	Mar. 31, 2014
Lease commitments	'
	21. Lease commitments:
	NIDEC leases certain assets under capital lease and operating lease arrangements. An analysis of leased assets under capital leases is as follows:
		Yen in millions
		March 31
	Class of property	2013			2014
	Machinery and equipment	¥	6,950		¥	7,336
	Other leased assets		65			109
	Less—Accumulated amortization		(1,345	)		(2,511	)
		¥	5,670		¥	4,934
	Amortization expenses under capital leases for the years ended March 31, 2012, 2013 and 2014 were ¥835 million, ¥524 million and ¥1,305 million, respectively.
	The future minimum lease payments under capital leases together with the present value of the net minimum lease payments as of March 31, 2014 are as follows:
		Yen in
		millions
	Year ending March 31:
	2015	¥	1,810
	2016		2,019
	2017		658
	2018		563
	2019		114
	2020 and thereafter		9
	Total minimum lease payments		5,173
	Less—Amount representing interest		(312	)
	Present value of net minimum lease payments		4,861
	Less—Current obligations		(1,667	)
	Long-term capital lease obligations	¥	3,194
	Rental expenses under operating leases for the years ended March 31, 2012, 2013 and 2014 were ¥1,526 million, ¥2,719 million and ¥2,586 million, respectively.
	The minimum rental payments required under operating leases relating primarily to land, buildings and equipment having initial or remaining non-cancelable lease terms in excess of one year as of March 31, 2014 are as follows:
		Yen in
		millions
	Year ending March 31:
	2015	¥	2,319
	2016		1,757
	2017		1,197
	2018		996
	2019		965
	2020 and thereafter		1,941
	Total minimum future rentals	¥	9,175
	NIDEC is a lessor in direct financing leases and operating leases for which a portion of the land, office and manufacturing facilities is subleased over various terms. The direct financing leases did not have a material impact on our consolidated financial position or results of operations.
	Rental revenues under operating leases for the years ended March 31, 2012, 2013 and 2014 were ¥373 million, ¥412 million and ¥175 million, respectively.
	The future minimum lease payments to be received under operating leases that have remaining non-cancelable terms as of March 31, 2014 are as follows:
		Yen in
		millions
	Year ending March 31:
	2015	¥	31
	2016		25
	2017		25
	2018		26
	2019		26
	2020 and thereafter		91
	Total minimum future rentals	¥	224

Flooding_in_Thailand

Flooding in Thailand	12 Months Ended
	Mar. 31, 2014
Flooding in Thailand	'
	22. Flooding in Thailand:
	The flooding in Thailand that occurred in October 2011 caused water damage to buildings, machinery, and other property, plant and equipment as well as inventories at some of NIDEC’s subsidiaries. For the year ended March 31, 2012, NIDEC has recognized a loss of ¥17,269 million, which comprises ¥13,730 million for property, plant and equipment and ¥3,539 million for inventory associated with water damage. For the years ended March 31, 2013 and 2014, NIDEC has not recognized a loss.
	NIDEC has insurance policies which cover certain damage directly caused by the flooding in Thailand. The insurance policies cover the damage associated with fixed assets and inventories. NIDEC has recognized insurance recoveries up to fair value or replacement cost that was approved by insurance company at some of NIDEC’s subsidiaries. As a result, NIDEC has recorded a net gain of ¥5,932 million and ¥4,027 million in operating income for the year ended March 31, 2012 and 2013, respectively.

Other_commitments_and_continge

Other commitments and contingencies, concentrations and factors that may affect future operations	12 Months Ended
	Mar. 31, 2014
Other commitments and contingencies, concentrations and factors that may affect future operations	'
	23. Other commitments and contingencies, concentrations and factors that may affect future operations:
	Commitments -
	Commitments outstanding at March 31, 2014 for the purchase of property, plant and equipment and other assets approximated ¥2,425 million.
	Contingencies -
	NIDEC has guaranteed approximately ¥60 million of bank loans for employees in connection with their housing costs at March 31, 2014. If an employee defaults on his/her loan payments, NIDEC would be liable under the guarantee. The maximum undiscounted amount of NIDEC’s obligation to make future payments in the event of defaults is approximately ¥60 million. The current carrying amount of the liabilities for NIDEC’s obligations under the guarantee is zero because it is not possible to estimate the amount of loss from employee’s defaults or range of the possible loss at this time.
	NIDEC is contingently liable under bid bonds, advance payment bonds, performance bonds, warranty bonds and payment bonds, totaling ¥6,967 million as of March 31, 2014, primarily for guarantees of our performance on projects currently in execution or under warranty. No material claims have been made against guarantees, and based on our past experience and current expectations, NIDEC does not anticipate any material claims.
	Concentration of risk -
	NIDEC is dependent on a number of large customers for a substantial portion of NIDEC’s net sales. Sales to NIDEC’s two largest customers represented approximately 22%, 20% and 17% of consolidated net sales for the years ended March 31, 2012, 2013 and 2014, respectively. Sales to NIDEC’s largest customer were approximately 12%, 11% and 9% of consolidated net sales for the years ended March 31, 2012, 2013 and 2014, respectively. Accounts receivable are financial instruments that expose NIDEC to a concentration of credit risk. At March 31, 2013, the two largest customers with outstanding accounts receivable balances totaled ¥19,534 million, or 13% of the gross accounts receivable, compared to ¥17,706 million, or 10% of the gross accounts receivable, at March 31, 2014. If any one or group of these customer’s receivable balances should be deemed uncollectable, it would have a materially adverse effect on NIDEC’s results of operations and financial condition.
	Product warranty –
	NIDEC guarantees the performance of products delivered and services rendered for a certain period or term. Estimates for warranty cost are made based on historical warranty claim experience. The changes in product warranty liability for the years ended March 31, 2013 and 2014 are summarized as follows:
		Yen in millions
		March 31
		2013			2014
	Balance at beginning of year	¥	971		¥	2,201
	Addition		1,626			2,021
	Utilization		(664	)		(1,080	)
	Foreign exchange impact		268			(106	)
	Balance at end of year	¥	2,201		¥	3,036

Discontinued_Operations

Discontinued Operations	12 Months Ended
	Mar. 31, 2014
Discontinued Operations	'
	24. Discontinued Operations
	As of March 31, 2012, NIDEC discontinued the lens actuator (“LAC”) business, the tape drive and disk drive mechanism (“PGN”) business included within the “NSNK” reportable segment, and the compact digital camera lens unit (“CLU”) business included within the “NCPL” reportable segment, in order to improve profitability by prioritizing NIDEC’s investment of management resources to the development and production of new products and areas with more potential for growth than the LAC, PGN and CLU businesses. Total exit costs of the LAC, PGN and CLU businesses were ¥5,800 million (net of tax ¥4,412 million), which includes an impairment loss of ¥2,045 million of goodwill, loss on disposal of inventories and fixed assets, and other closing costs.
	The operating results of the LAC, PGN and CLU businesses and exit costs with related taxes were recorded as “net loss on discontinued operations” in the consolidated statement of income in accordance with ASC 205-20 “Presentation of Financial Statements-Discontinued Operations”. All prior period information has been reclassified to be consistent with the current period presentation.
	Operating results of discontinued operations for the year ended March 31, 2012 were as follows:
		Yen in millions
		For the year ended
		March 31, 2012
		LAC			PGN			CLU			Total
		business			business			business
	Net sales	¥	1,576		¥	1,365		¥	2,674		¥	5,615
	Loss on discontinued operations before income taxes	¥	(2,203	)	¥	(1,817	)	¥	(3,776	)	¥	(7,796	)
	Income taxes		(269	)		129			168			28
	Loss on discontinued operations	¥	(2,472	)	¥	(1,688	)	¥	(3,608	)	¥	(7,768	)

Segment_information

Segment information	12 Months Ended
	Mar. 31, 2014
Segment information	'
	25. Segment information:
	(1) Enterprise-wide information:
	Product information –
	The following table provides product information for the years ended March 31, 2012, 2013 and 2014:
			Yen in millions
			For the year ended
			March 31
			2012			2013			2014
	Net sales:
	Small precision motors:
	Hard disk drives spindle motors		¥	176,932		¥	165,427		¥	185,506
	Other small precision motors			154,505			154,297			177,007
	Sub-total			331,437			319,724			362,513
	Automotive, appliance, commercial and industrial products			208,529			248,464			345,236
	Machinery			64,904			63,526			86,955
	Electronic and optical components			69,377			69,188			72,845
	Others			8,073			8,368			7,560
	Consolidated total		¥	682,320		¥	709,270		¥	875,109
	The “Hard disk drives spindle motors” group of products consists of hard disk drives spindle motors for 3.5-inch, 2.5-inch, and 1.8-inch hard disk drives.
	The “Other small precision motors” group of products consists of brushless motors for many types of products, including optical disk drive motors, OA equipment motors, brushless fans, which are used in many types of products, including computers and game machines for the purpose of lowering the temperature of central processing units in these products, automotive fans, vibration motors for mobile phones, brush DC motors for many types of products, stepping motors, and motor application products.
	The “Automotive, appliance, commercial and industrial products” group of products consists of home appliances, commercial and industrial motors and related products, automotive motors, and automotive components.
	The “Machinery” group of products consists of test systems, measuring equipment, power transmission equipment, factory automation systems, card readers, industrial robots and press machines.
	The “Electronic and optical components” group of products consists of camera shutters, camera lens units, switches, trimmer potentiometers, processing and precision plastic mold products.
	“Others” consists of other services and other components.
	Geographic information –
	Revenues from external customers, which are attributed to countries based on the location of the Company or the subsidiaries that transacted with the external customer for the years ended March 31, 2012, 2013 and 2014, and long-lived assets as of March 31, 2013 and 2014 are as follows:
			Yen in millions
			For the year ended
			March 31
			2012			2013			2014
	Net sales:
	Japan		¥	260,470		¥	213,169		¥	238,278
	U.S.A.			71,317			99,260			132,117
	Singapore			40,595			55,712			63,950
	Thailand			75,908			81,678			85,435
	The Philippines			19,683			18,543			24,506
	China			148,553			150,631			197,134
	Other			65,794			90,277			133,689
	Consolidated total		¥	682,320		¥	709,270		¥	875,109
			Yen in millions
			March 31
			2013			2014
	Long-lived assets:
	Japan		¥	86,612		¥	96,239
	U.S.A.			21,047			23,046
	Singapore			1,899			1,337
	Thailand			42,418			37,925
	The Philippines			11,838			12,904
	China			56,756			65,007
	Other			57,407			62,423
	Consolidated total		¥	277,977		¥	298,881
	(2) Operating segment information:
	The operating segments reported below are defined as components of an enterprise for which separate financial information is available and regularly reviewed by NIDEC’s chief operating decision maker. NIDEC’s chief operating decision maker utilizes various measurements to assess segment performance and allocate resources to segments.
	The Nidec Corporation segment comprises Nidec Corporation in Japan, which primarily develops and sells hard disk drives spindle motors, DC motors, fans, and automotive products.
	The Nidec Electronics (Thailand) segment comprises Nidec Electronics (Thailand) Co., Ltd., a subsidiary in Thailand, and its consolidated subsidiaries, which primarily produce and sell hard disk drive motors. This segment also includes other subsidiaries in Asia which produce components for hard disk drives.
	The Nidec (Zhejiang) segment comprises Nidec (Zhejiang) Corporation, a subsidiary in China, which primarily produces and sells hard disk drive motors.
	The Nidec (Dalian) segment comprises Nidec (Dalian) Limited, a subsidiary in China, which primarily produces and sells DC motors and fans but excludes its automotive products business.
	The Nidec Singapore segment comprises Nidec Singapore Pte. Ltd., a subsidiary in Singapore, and its consolidated subsidiary, which primarily sell hard disk drive motors, DC motors and fans.
	The Nidec (H.K.) segment comprises Nidec (H.K.) Co., Ltd., a subsidiary in Hong Kong, and its consolidated subsidiaries, which primarily sell hard disk drive motors, DC motors and fans.
	The Nidec Philippines segment comprises Nidec Philippines Corporation, a subsidiary in the Philippines, and its consolidated subsidiary, which primarily produce and sell hard disk drive motors.
	The Nidec Sankyo segment comprises Nidec Sankyo Corporation, a subsidiary in Japan, and its consolidated subsidiaries, which primarily produce and sell DC motors, machinery, and electronic parts.
	The Nidec Copal segment comprises Nidec Copal Corporation, a subsidiary in Japan, and its consolidated subsidiaries, which primarily produce and sell optical and electronic parts and machinery.
	The Nidec Tosok segment comprises Nidec Tosok Corporation, a subsidiary in Japan, and its consolidated subsidiaries, which primarily produce and sell automotive parts.
The Nidec Copal Electronics segment comprises Nidec Copal Electronics Corporation, a subsidiary in Japan, and its consolidated subsidiaries, which primarily produce and sell electronic parts.
The Nidec Techno Motor segment comprises Nidec Techno Motor Corporation, a subsidiary in Japan, and its consolidated subsidiaries, which primarily produce and sell commercial and industrial products.
The Nidec Motor segment comprises Nidec Motor Corporation and other subsidiaries in North America, which are subsidiaries of Nidec US Holdings Corporation, an intermediate holding company in the United States, as well as other subsidiaries in Latin America, Asia and Europe, which primarily produce and sell home appliance, commercial and industrial products. This segment also includes Nidec ASI, Avtron and Kinetek, which were newly consolidated for the year ended March 31, 2013.
The Nidec Motors & Actuators segment comprises Nidec Motors & Actuators(Germany) GmbH in Germany, other subsidiaries in Europe and North America, and other manufacturing subsidiaries in China, which primarily produce and sell automotive products.
The All Others segment comprises subsidiaries that are operating segments but not designated as reportable segments due to their immateriality.
NIDEC evaluates performance based on segmental profit and loss, which consists of sales and operating revenues less operating expenses. All segmental operating income or loss is accounted for under Japanese GAAP, except for Nidec Electronics (Thailand), Nidec (Zhejiang), Nidec (Dalian), Nidec Singapore, Nidec (H.K.), Nidec Philippines, Nidec Motor and Nidec Motors & Actuators. Therefore segmental data has not been prepared under U.S. GAAP on a basis that is consistent with the consolidated financial statements or on any other single basis that is consistent between segments. There are several differences between U.S. GAAP and the underlying accounting bases used by management, the principal differences that affect segmental operating income or loss are accounting for pension and severance costs, and leases. Our segmental operating income or loss is presented in accordance with financial reporting principles and practices generally accepted in Japan. Management believes that the monthly segmental information is available on a timely basis, and that it is sufficiently accurate at the segment income or loss level for management’s purposes.
The following tables show net sales to external customers and other financial information by operating segment for the years ended March 31, 2012, 2013 and 2014:
		Yen in millions
		For the year ended
		March 31
		2012			2013			2014
Net sales to external customers:
Nidec Corporation		¥	46,901		¥	23,748		¥	27,599
Nidec Electronics (Thailand)			64,226			63,349			67,623
Nidec (Zhejiang)			26,430			21,109			18,017
Nidec (Dalian)			4,269			3,648			1,940
Nidec Singapore			34,220			50,039			57,893
Nidec (H.K.)			50,748			52,028			69,890
Nidec Philippines			15,326			14,707			19,573
Nidec Sankyo			78,589			73,201			98,564
Nidec Copal			51,124			49,627			47,023
Nidec Tosok			33,358			31,090			36,854
Nidec Copal Electronics			29,098			26,845			31,295
Nidec Techno Motor			40,058			39,940			50,691
Nidec Motor			83,999			119,093			175,854
Nidec Motors & Actuators			44,748			44,707			64,420
All Others			78,268			96,236			106,996
Total			681,362			709,367			874,232
Adjustments *1			958			(97	)		877
Consolidated total		¥	682,320		¥	709,270		¥	875,109
*1	US GAAP adjustments primarily relate to the difference between recognition of revenue at the time of shipment and at the time of customer receipt.
NIDEC had sales to two customers of ¥151,253 million for the year ended March 31, 2012, and sales to one customer of ¥74,897 million for the year ended March 31, 2013 within the Nidec Corporation, Nidec Electronics (Thailand), Nidec (Zhejiang), Nidec Singapore, Nidec (H.K.) and “All Others” segments, that exceeded 10% of NIDEC’s net sales. There was no certain customer group which exceeded 10% of the consolidated net sales for the year ended March 31, 2014.
		Yen in millions
		For the year ended
		March 31
		2012			2013			2014
Net sales to other operating segments:
Nidec Corporation		¥	100,064		¥	108,282		¥	138,354
Nidec Electronics (Thailand)			36,649			35,492			43,982
Nidec (Zhejiang)			3,617			2,977			5,011
Nidec (Dalian)			15,471			11,117			10,559
Nidec Singapore			448			709			749
Nidec (H.K.)			1,162			1,734			1,339
Nidec Philippines			24,390			25,682			29,266
Nidec Sankyo			396			300			312
Nidec Copal			2,318			2,093			2,318
Nidec Tosok			150			190			171
Nidec Copal Electronics			20			20			11
Nidec Techno Motor			952			3,143			4,041
Nidec Motor			30			154			80
Nidec Motors & Actuators			11,607			15,170			20,213
All Others			53,061			55,834			73,029
Total			250,335			262,897			329,435
Intersegment elimination			(250,335	)		(262,897	)		(329,435	)
Consolidated total			—			—			—
		Yen in millions
		For the year ended
		March 31
		2012			2013			2014
Operating income or loss:
Nidec Corporation		¥	7,497		¥	(4,856	)	¥	4,865
Nidec Electronics (Thailand)			15,027			10,525			12,781
Nidec (Zhejiang)			774			(2,689	)		(243	)
Nidec (Dalian)			431			(409	)		475
Nidec Singapore			781			1,115			709
Nidec (H.K.)			359			146			483
Nidec Philippines			7,799			4,883			6,037
Nidec Sankyo			7,414			4,181			10,392
Nidec Copal			6,384			(3,192	)		(1,323	)
Nidec Tosok			3,140			1,715			3,186
Nidec Copal Electronics			4,194			3,277			5,288
Nidec Techno Motor			4,591			4,168			6,671
Nidec Motor			2,111			723			9,314
Nidec Motors & Actuators			3,126			3,447			5,334
All Others			11,201			10,540			18,911
Total			74,829			33,574			82,880
Reclassification *1			(3,072	)		(17,606	)		2,055
U.S. GAAP adjustments and Others *2			(1,476	)		(537	)		(1,133	)
Consolidation adjustments mainly related to elimination of intersegment income or loss			2,789			2,167			1,266
		¥	73,070		¥	17,598		¥	85,068
*1	Some items are reclassified from other expenses (income) and included in operating expenses (income). Main reclassification is income or loss from sales or disposals of fixed assets for the year ended March 31, 2012, 2013 and 2014.
*2	Others is mainly from the amortization of identifiable intangible assets related to business combinations for the years ended March 31, 2012, 2013 and 2014.
		Yen in millions
		For the year ended
		March 31
		2012			2013			2014
Depreciation:
Nidec Corporation		¥	995		¥	917		¥	921
Nidec Electronics (Thailand)			5,085			5,572			5,502
Nidec (Zhejiang)			1,231			1,196			618
Nidec (Dalian)			802			914			359
Nidec Singapore			70			133			197
Nidec (H.K.)			6			7			6
Nidec Philippines			2,598			2,750			2,732
Nidec Sankyo			3,715			3,773			4,102
Nidec Copal			3,115			3,806			4,444
Nidec Tosok			2,660			2,930			3,775
Nidec Copal Electronics			1,150			1,318			1,283
Nidec Techno Motor			1,491			1,890			2,573
Nidec Motor			3,892			6,481			9,171
Nidec Motors & Actuators			1,423			1,470			2,186
All Others			4,297			5,265			6,537
Total			32,530			38,422			44,406
U.S. GAAP adjustments *1 and Others *2			(1,019	)		(3,487	)		(4,921	)
Consolidated total		¥	31,511		¥	34,935		¥	39,485
*1	Some leased assets are not capitalized in the operating segments but are capitalized under U.S. GAAP.
*2	The amount of each segment includes amortization of intangible assets. Others mainly represent adjustments to exclude the amortization of intangible assets in order to reconcile amounts to consolidated total of depreciation in consolidated statements of cash flows.
		Yen in millions
		March 31
		2013			2014
Segment assets:
Nidec Corporation		¥	565,451		¥	628,338
Nidec Electronics (Thailand)			91,784			116,476
Nidec (Zhejiang)			13,897			12,112
Nidec (Dalian)			24,159			20,763
Nidec Singapore			21,590			27,689
Nidec (H.K.)			15,678			22,458
Nidec Philippines			37,084			49,569
Nidec Sankyo			107,393			125,929
Nidec Copal			62,376			55,166
Nidec Tosok			43,566			50,221
Nidec Copal Electronics			38,684			42,115
Nidec Techno Motor			42,508			49,703
Nidec Motor			178,429			197,315
Nidec Motors & Actuators			46,601			68,405
All Others			158,388			217,075
Total			1,447,588			1,683,334
Elimination of intersegment assets, net of taxes			(579,766	)		(626,822	)
Identifiable intangible assets and other fair value adjustments			12,502			11,626
Goodwill			132,775			154,927
U.S.GAAP adjustments and Others *1			(7,682	)		(57,147	)
Consolidated total		¥	1,005,417		¥	1,165,918
*1	Others is mainly due to the reclassification of deferred tax assets and liabilities on consolidation.
		Yen in millions
		For the year ended
		March 31
		2013			2014
Capital expenditure for segment assets:
Nidec Corporation		¥	1,991		¥	1,884
Nidec Electronics (Thailand)			14,588			1,232
Nidec (Zhejiang)			710			712
Nidec (Dalian)			2,372			972
Nidec Singapore			417			9
Nidec (H.K.)			5			6
Nidec Philippines			1,876			3,368
Nidec Sankyo			4,777			3,712
Nidec Copal			9,539			2,427
Nidec Tosok			5,814			9,432
Nidec Copal Electronics			984			826
Nidec Techno Motor			5,144			3,549
Nidec Motor			3,594			4,134
Nidec Motors & Actuators			1,845			3,019
All Others			7,712			5,015
Consolidated total		¥	61,368		¥	40,297
NIDEC did not have significant non-cash items other than depreciation in reported profit. Intersegment sales were made at prices that approximate current market value.

Subsequent_events

Subsequent events	12 Months Ended
	Mar. 31, 2014
Subsequent events	'
	26. Subsequent events:
	Dividends for the fiscal year ended March 31, 2014
	Subsequent to March 31, 2014, the Company’s Board of Directors declared a cash dividend of ¥7,585 million payable on June 3, 2014 to stockholders as of March 31, 2014.
	A Share Exchange Agreement to Make Nidec Copal Electronics Corporation a Wholly Owned Subsidiary of Nidec Corporation
	On April 22, 2014, NIDEC decided, at a meeting of the Board of Directors, to enter into a share exchange transaction (the “Share Exchange”) with Nidec Copal Electronics Corporation (“NCEL”) to make NCEL a wholly owned subsidiary, and entered into a share exchange agreement with NCEL on the same day.
	1)	Reason for the share exchange	The Company and NCEL have determined that, in order for NCEL to further grow its business and improve its profitability, it is imperative that management decisions be made promptly and flexibly, resources be fully shared with the Company, investments by both the Company and NCEL produce better results, and an operational structure be established where NCEL is fully integrated with the Company to achieve better performance.
	2)	Share exchange procedure and effective date	The Share Exchange will become effective on October 1, 2014, per approval of NCEL’s shareholders at the ordinary general meeting held on June 20, 2014. The Company uses a simplified share exchange procedure in accordance with Article 796, Paragraph 3, of the Company Act, without obtaining the approval of its shareholders for the Share Exchange.
	3)	Ratio applied to the allocation of shares	For each share of NCEL common stock, 0.138 shares of the Company’s common stock will be allocated.
			In the event of a significant change to the factors and assumptions used for calculating the ratio, the above share exchange ratio may be modified upon the agreement of the Company and NCEL.
	4)	Number of shares of the Company allocated in the share exchange	The Company expects to allocate 3,160,584 shares (tentative) of its common stock in the Share Exchange. The Company intends to use shares of its common stock held in treasury, and does not intend to issue any new shares, for the Share Exchange.
	A Share Exchange Agreement to Make Nidec-Read Corporation a Wholly Owned Subsidiary of Nidec Corporation
	On April 22, 2014, NIDEC decided, at a meeting of the Board of Directors, to enter into a share exchange transaction (the “Share Exchange”) with Nidec-Read Corporation (“NRCJ”) to make NRCJ a wholly owned subsidiary, and entered into a share exchange agreement with NRCJ on the same day.
	1)	Reason for the share exchange	The Company and NRCJ have determined that, in order for NRCJ to further grow its business and improve its profitability, it is imperative that management decisions be made promptly and flexibly, resources be fully shared with the Company, investments by both the Company and NRCJ produce better results, and an operational structure be established where NRCJ is fully integrated with the Company to achieve better performance.
	2)	Share exchange procedure and effective date	The Share Exchange will become effective on October 1, 2014, per approval of NRCJ’s shareholders at the ordinary general meeting held on June 17, 2014. The Company uses a simplified share exchange procedure in accordance with Article 796, Paragraph 3, of the Company Act, without obtaining the approval of its shareholders for the Share Exchange.
	3)	Ratio applied to the allocation of shares	For each share of NRCJ common stock, 0.243 shares of the Company’s common stock will be allocated.
			In the event of a significant change to the factors and assumptions used for calculating the ratio, the above share exchange ratio may be modified upon the agreement of the Company and NRCJ.
	4)	Number of shares of the Company allocated in the share exchange	The Company expects to allocate 1,421,513 shares (tentative) of its common stock in the Share Exchange. The Company intends to use shares of its common stock held in treasury, and does not intend to issue any new shares, for the Share Exchange.

Quarterly_Financial_Data_for_t

Quarterly Financial Data for the year ended March 31, 2014	12 Months Ended
	Mar. 31, 2014
Quarterly Financial Data for the year ended March 31, 2014	'
	27. Quarterly Financial Data for the year ended March 31, 2014: (Unaudited)
			Yen in millions
			First		Second		Third		Fourth		Total
			Quarter		Quarter		Quarter		Quarter
	Net sales		¥	211,276	¥	218,358	¥	217,091	¥	228,384	¥	875,109
	Income before income taxes			17,366		21,075		24,084		22,139		84,664
	Net income attributable to Nidec Corporation		¥	13,346	¥	13,757	¥	15,950	¥	13,351	¥	56,404
			Yen
	Net income attributable to Nidec Corporation per share:
	Basic *1			49.73		51.26		57.84		48.41		207.31
	Diluted *1			46.42		47.85		54.24		45.39		193.96
	Notes:
	*1:	Earnings-per-share amounts for each quarter are computed independently. As a result, their sum may not equal the total year earnings-per-share amounts.

Summary_of_significant_account1

Summary of significant accounting policies (Policies)	12 Months Ended
	Mar. 31, 2014
Estimates	'
	Estimates -
	The preparation of NIDEC’s consolidated financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and contingent assets and liabilities at the date of the financial statements, as well as the reported amounts of revenues and expenses during the reporting period. Some of the more significant estimates include the valuation of inventories, allowance for doubtful accounts, depreciation and amortization of long-lived assets, valuation allowance for deferred tax assets, valuation of investment securities, fair value of financial instruments, uncertain tax positions, pension liabilities, the recoverability of long-lived assets and goodwill, and fair value of assets acquired and liabilities assumed. Actual results could differ from those estimates.
Basis of consolidation and accounting for investments in affiliated companies	'
	Basis of consolidation and accounting for investments in affiliated companies -
	The consolidated financial statements include the accounts of the Company and those of its majority-owned subsidiary companies. All significant intercompany transactions and accounts have been eliminated. Companies over which NIDEC exercises significant influence, but which it does not control, are classified as affiliated companies and accounted for using the equity method. Consolidated net income includes NIDEC’s equity in current earnings (losses) of such companies, after elimination of unrealized intercompany profits.
	On occasion, NIDEC may acquire additional shares of the voting rights of a consolidated subsidiary or dispose of a part of those shares or a Nidec consolidated subsidiary may issue its shares to third parties. With respect to such transactions, all transactions for changes in a parent’s ownership interest in a subsidiary that do not result in the subsidiary ceasing to be a subsidiary are recognized as equity transactions.
Translation of foreign currencies	'
	Translation of foreign currencies -
	Non monetary asset and liability accounts of foreign subsidiaries and affiliates are translated into Japanese yen at the year-end exchange rates and all income and expense accounts are translated at exchange rates that approximate those prevailing at the time of the transactions. The resulting translation adjustments are included as a component of accumulated other comprehensive income in shareholders’ equity.
	Monetary assets and liabilities denominated in foreign currencies are translated at the year-end exchange rates and the resulting transaction gains or losses are taken into income.
Cash and cash equivalents	'
	Cash and cash equivalents -
	Cash and cash equivalents include all highly liquid investments, with original maturities of three months or less that are readily convertible to known amounts of cash and are so near maturity that they present insignificant risk of changes in value because of changes in interest rates.
Inventories	'
	Inventories -
	Inventories are stated at the lower of cost or market. Cost is determined principally on the weighted average cost basis. Cost includes the cost of materials, labor and applied factory overhead. Projects in progress, which mainly relate to production of factory automation equipment based on contracts with customers, are stated at the lower of cost or market, cost being determined as the accumulated production cost.
Marketable securities	'
	Marketable securities -
	Marketable securities consist of equity securities that are listed on recognized stock exchanges and debt securities. Equity securities designated as available-for-sale are carried at fair value with changes in unrealized gains or losses included as a component of accumulated other comprehensive income in shareholders’ equity, net of applicable taxes. Realized gains and losses are determined on the average cost method and are reflected in the statement of income. Other than temporary declines in market value of individual securities classified as available-for-sale are charged to income in the period the loss occurs. Debt securities designated as held-to-maturity securities are recorded at amortized cost, adjusted for the amortization or accretion of premiums or discounts.
Derivative financial instruments	'
	Derivative financial instruments -
	NIDEC manages the exposures of fluctuations in foreign exchange rate, interest rate and commodity prices through the use of derivative financial instruments which include foreign exchange forward contracts, currency option contracts, interest rate swap agreements and commodity future contracts. NIDEC does not hold derivative financial instruments for trading purposes.
	Derivatives are accounted for under ASC 815, “Derivatives and Hedging.” All derivatives are recorded as either assets or liabilities on the balance sheet and measured at fair value. Changes in the fair value of derivatives are charged in current earnings. However certain derivatives may qualify for hedge accounting as a cash flow hedge, if the hedging relationship is expected to be highly effective in achieving offsetting of cash flows of the hedging instruments and hedged items. Under hedge accounting, changes in the fair value of the effective portion of these derivatives designated as cash flow hedge derivatives are deferred in accumulated other comprehensive income and charged to earnings when the underlying transaction being hedged occurs.
	NIDEC designates certain foreign exchange forward contracts, interest rate swap agreements and commodity future contracts as cash flow hedges. NIDEC formally documents all relationships between hedging instruments and hedged items, as well as its risk management objective and strategy for undertaking various hedge transactions. This process includes linking all derivatives designated as cash flow hedges to specific assets and liabilities on the balance sheet or forecasted transactions. NIDEC also formally assesses, both at the hedge’s inception and on an ongoing basis, whether the derivatives that are used in hedging transactions are highly effective in offsetting cash flows of hedged items. When it is determined that a derivative is not a highly effective hedge or that it has ceased to be a highly effective hedge, NIDEC discontinues hedge accounting prospectively. When a cash flow hedge is discontinued, the previously recognized net derivative gains or losses remain in accumulated other comprehensive income until the hedged transaction occurs, unless it is probable that the forecasted transaction will not occur at which point the derivative gains or losses are reclassified into earnings immediately.
Property, plant and equipment	'
	Property, plant and equipment -
	Property, plant and equipment are stated at cost. Major renewals and improvements are capitalized; minor replacements, maintenance and repairs are charged to expense in the year incurred.
	Depreciation of property, plant and equipment is computed on the straight-line method at rates based on the estimated useful lives of the assets. Estimated useful lives range from 7 to 47 years for factories to produce NIDEC’s products, 50 years for the head office and sales offices, from 3 to 18 years for leasehold improvements, and from 2 to 15 years for machinery and equipment.
	Depreciation expense amounted to ¥31,511 million, ¥34,935 million, and ¥39,485 million for the years ended March 31, 2012, 2013 and 2014, respectively.
Lease	'
	Lease-
	NIDEC capitalizes leases and related obligations when any of the four criteria are met within the guidance of ASC 840 “Leases”. Under ASC840, these leases and related obligations are capitalized at the commencement of the lease at the lower of the fair value of the leased property and the present value of the minimum lease payments.
Goodwill and other intangible assets	'
	Goodwill and other intangible assets -
	Goodwill and other intangible assets are accounted for under ASC350, “Intangibles—Goodwill and Other”.
	Goodwill acquired in business combinations is not amortized but tested annually for impairment. NIDEC tests for impairment at the reporting unit level on January 1st of each year. In addition, NIDEC tests for impairment between annual tests if an event occurs or circumstances change that would more likely than not reduce the fair value of a reporting unit below its carrying amount. This test is a two-step process. The first step of the goodwill impairment test, used to identify potential impairment, compares the fair value of the reporting unit with its carrying amount, including goodwill. If the fair value, which is based on discounted future cash flows, exceeds the carrying amount, goodwill is not considered impaired. If the carrying amount exceeds the fair value, the second step must be performed to measure the amount of the impairment loss, if any. The second step compares the implied fair value of the reporting unit’s goodwill with the carrying amount of that goodwill.
	Other intangible assets include proprietary technology and customer relationships, as well as software and other intangible assets acquired in business combinations. Intangible assets with an indefinite life are not subject to amortization and are tested for impairment once on January 1st of each year or more frequently if an event occurs or circumstances change. Intangible assets with a definite life are amortized on a straight-line basis over their estimated useful lives. The weighted average amortization period for proprietary technology, customer relationships and software are 12 years, 18 years and 5 years, respectively.
Long-lived assets	'
	Long-lived assets -
	NIDEC reviews its long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset group may not be recoverable. An impairment loss would be recognized when the carrying amount of an asset group exceeds the estimated undiscounted future cash flows expected to result from the use of the asset group and its eventual disposition. The amount of the impairment loss to be recorded is calculated as the excess of the assets group’s carrying value over its fair value. Long-lived assets that are to be disposed of other than by sale are considered to be held and used until the disposal. Long-lived assets that are to be disposed of by sale are reported at the lower of their carrying value or fair value less costs to sell. Reductions in carrying value are recognized in the period in which long-lived assets are classified as held for sale.
Revenue recognition	'
	Revenue recognition -
	NIDEC recognizes revenue when persuasive evidence of an arrangement exists, delivery has occurred, the sales price is fixed or determinable and collectibility is reasonably assured. For small precision motors, automotive, appliance, commercial and industrial products and electronic and optical components, these criteria are generally met at the time a product is delivered to the customers’ site which is the time the customer has taken title to the product and the risk and rewards of ownership have been substantively transferred. These conditions are met at the time of delivery to customers in domestic sales (FOB destination) and at the time of shipment for export sales (FOB shipping point). Revenue for machinery sales is recognized upon receipt of final customer acceptance. At the time the related revenue is recognized, NIDEC makes provisions for estimated product returns. Revenue from a part of sales of automotive, appliance, commercial and industrial products under long-term construction type arrangements are recognized under the percentage-of-completion method. Under the percentage-of-completion method, revenue is recognized as a percentage of estimated total revenue that incurred costs to date bear to estimated total costs after giving effect to estimates of costs to complete based upon the most recent information.
Research and development expenses	'
	Research and development expenses -
	Research and development expenses, mainly consisting of personnel and depreciation expenses at research and development branches, are charged to operations as incurred.
Advertising costs	'
	Advertising costs -
	Advertising and sales promotion costs are expensed as incurred. Advertising costs were ¥228 million, ¥296 million, and ¥477 million for the years ended March 31, 2012, 2013 and 2014, respectively.
Income taxes	'
	Income taxes -
	The provision for income taxes is computed based on the pretax income included in the consolidated statement of income. The asset and liability approach is used to recognize deferred tax assets and liabilities for the expected future tax consequences of temporary differences between the carrying amounts and the tax bases of assets and liabilities. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. Valuation allowances are recorded to reduce deferred tax assets when it is more likely than not that a tax benefit will not be realized.
	NIDEC recognizes the financial statement effects of tax positions when it is 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 percent likely of being realized upon settlement. Interest and penalties accrued related to unrecognized tax benefits are included in other, net in the consolidated statements of income.
Earnings per share	'
	Earnings per share -
	Basic net income per common share is calculated by dividing net income by the weighted-average number of shares outstanding during the reported period. The calculation of diluted net income per common share is similar to the calculation of basic net income per share, except that the weighted-average number of shares outstanding includes the additional dilution from potential common stock equivalents such as convertible bonds and options.
Reclassification	'
	Reclassification
	Certain reclassifications of previously reported amounts have been made to the consolidated statements of income and cash flows for the years ended March 31, 2012 and 2013 to conform to the current year presentation.
	As of March 31, 2012, NIDEC discontinued its lens actuator business and its tape drive and disk drive mechanism business included within the Nidec Sankyo reportable segment, and its compact digital camera lens unit business included within the Nidec Copal reportable segment. The operating results of the discontinued businesses and exit costs with related taxes were recorded as “Loss on discontinued operations” in the consolidated statement of income in accordance with ASC 205-20, “Presentation of Financial Statements-Discontinued Operations”.
Accounting Changes	'
	Accounting Changes
	As of April 1, 2013, NIDEC adopted FASB Accounting Standards Codification™ (ASC) 350 “Intangibles-Goodwill and Other” updated by Accounting Standards Update (ASU) No. 2012-02 “Testing Indefinite-Lived Intangible Assets for Impairment.” ASU 2012-02 allows an entity the option of performing a qualitative assessment before calculating the fair value of an indefinite-lived intangible asset and performing the quantitative impairment test. If an entity determines, on the basis of qualitative factors, that it is more likely than not that the asset is impaired, the quantitative impairment test would be required. The adoption of this standard did not have material impact on NIDEC’s consolidated financial position, results of operations and liquidity.
	As of April 1, 2013, NIDEC adopted FASB ASC 220 “Comprehensive income.” updated by ASU No. 2013-02 “Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income.” ASU 2013-02 requires an entity 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 but only if the amount reclassified is required under U.S. GAAP to be reclassified to net income in its entirety in the same reporting period. The standard is provision for disclosure. The adoption of this standard did not have any impact on NIDEC’s consolidated financial position, results of operations and liquidity.
Recent Accounting Pronouncements to be adopted in future periods	'
	Recent Accounting Pronouncements to be adopted in future periods
	In July 2013, the FASB issued ASU No. 2013-11, “Income taxes (Topic 740): Presentation of an Unrecognized Tax Benefit When a Net Operating Loss Carryforward, a Similar Tax Loss, or a Tax Credit Carryforward Exists.” ASU 2013-11 clarifies that an unrecognized tax benefit, or a portion of an unrecognized tax benefit, should be presented in the financial statements as a reduction to a deferred tax asset for a net operating loss carryforward, a similar tax loss, or a tax credit carryforward if such settlement is required or expected in the event the uncertain tax position is disallowed. In situations where a net operating loss carry forward, a similar tax loss, or a tax credit carryforward is not available at the reporting date under the tax law of the applicable jurisdiction or the tax of the jurisdiction does not require, and the entity does not intend to use, the deferred tax asset for such purpose, the unrecognized tax benefit should be presented in the financial statements as a liability and should not be combined with deferred tax assets. ASU 2013-11 is effective for reporting periods beginning after December 15, 2013. Early adoption and retrospective application are permitted. This standard is provision for disclosure. The adoption of this standard will not have any impact on NIDEC’s consolidated financial position, results of operations or liquidity.
	In April 2014, the FASB issued ASU No. 2014-08, “Presentation of Financial Statements (Topic 205) and Property, Plant, and Equipment (Topic 360): “Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity.” Under the new standard, a disposal of a component or a group of components of an entity is required to be reported in discontinued operations if the disposal represents a strategic shift that has (or will have) a major effect on an entity’s operations and financial results when the component meets the criteria to be classified as held for sale or is disposed. The amendments in this update also require additional disclosures about discontinued operations and disposal of an individually significant component of an entity that does not qualify for discontinued operations. ASU 2014-08 is effective for annual and interim periods beginning after December 15, 2014. Early adoption is permitted. The impact of the adoption of ASU 2014-08 on NIDEC’s consolidated financial position, results of operations and liquidity will depend on, and may be significant depending on, the size and nature of its future disposal.
	In May 2014, the FASB issued ASU No. 2014-09, “Revenue from Contracts with Customers (Topic 606)” Under the new standard, an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. An entity should recognize revenue when (or as) it satisfies a performance obligation by transferring a promised good or service to a customer, and the transaction price should be allocated to performance obligation in the contract. The new standard also requires an entity to disclose sufficient information to enable users of financial statements to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. ASU 2014-09 is effective for annual and interim periods beginning after December 15, 2016. Early application is not permitted. NIDEC is currently evaluating the potential impact from adopting ASU 2014-09 on its consolidated financial position, results of operations and liquidity.

Acquisitions_Tables

Acquisitions (Tables)	12 Months Ended
	Mar. 31, 2014
Summary of Estimated Fair Value of Assets Acquired and Liabilities Assumed at Acquisition Date	'
	The following table summarizes the estimated fair values of the assets acquired and liabilities assumed at the acquisition date.
		Yen in millions
		January 1,			March 31,
		2014			2014
		CMI			Elesys
	Cash and cash equivalents	¥	1,081		¥	5,759
	Accounts receivable		1,323			5,176
	Inventories		2,155			4,600
	Other current assets		683			1,483
	Property, plant and equipment		4,538			6,803
	Goodwill		2,114			9,668
	Intangible assets		55			58
	Other non-current assets		790			657
	Total assets acquired		12,739			34,204
	Accounts payable		(1,420	)		(6,618	)
	Other current liabilities		(2,834	)		(2,417	)
	Other non-current liabilities		(3,256	)		(849	)
	Total liabilities assumed		(7,510	)		(9,884	)
	Noncontrolling interests		(1	)		—
	Net assets acquired	¥	5,228		¥	24,320
Unaudited Pro Forma Results of Operations	'
	The following represents the unaudited pro forma results of operations of NIDEC for the years ended March 31, 2013 and 2014, as if the acquisition in these companies had occurred on April 1, 2012. The unaudited pro forma results of operations are presented for comparative purposes only and are not necessarily indicative of the results of operations that may occur in the future or that would have occurred had the acquisitions been in effect on the dates indicated.
		Yen in millions
		For the year ended March 31
		(Unaudited)
		2013			2014
	Pro forma net sales	¥	787,716		¥	928,910
	Pro forma net income		9,378			57,788
		Yen
	Pro forma net income attributable to Nidec Corporation per share
	—basic	¥	34,81		¥	212.4
	—diluted		32.32			198.72

Goodwill_and_other_intangible_1

Goodwill and other intangible assets (Tables)	12 Months Ended
	Mar. 31, 2014
Goodwill Allocated to Operating Segment	'
	The changes in the carrying amount of goodwill by operating reportable segment for the years ended March 31, 2012 and 2013 are as follows:
		Yen in millions
		Balance as of		Acquisition		Impairment		Translation			Balance as of
		April 1,				loss		adjustments			March 31,
		2012						and Others			2013
	Goodwill:
	Nidec Electronics (Thailand)	¥	6,109	¥	—	¥	—	¥	885		¥	6,994
	Nidec (Zhejiang)		912		—		—		132			1,044
	Nidec Sankyo		26,100		1,094		—		118			27,312
	Nidec Copal		16,462		—		—		—			16,462
	Nidec Tosok		1,107		—		—		(69	)		1,038
	Nidec Copal Electronics		6,561		—		—		—			6,561
	Nidec Techno Motor		2,049		—		—		—			2,049
	Nidec Motor		11,984		34,021		—		9,003			55,008
	Nidec Motors & Actuators		4,737		1,062		—		586			6,385
	All Others		4,504		4,785		—		633			9,922
		¥	80,525	¥	40,962	¥	—	¥	11,288		¥	132,775
	The changes in the carrying amount of goodwill by operating reportable segment for the years ended March 31, 2013 and 2014 are as follows:
		Yen in millions
		Balance as of		Acquisition		Impairment		Translation			Balance as of
		April 1,				loss		adjustments			March 31,
		2013						and Others			2014
	Goodwill:
	Nidec Electronics (Thailand)	¥	6,994	¥	—	¥	—	¥	651		¥	7,645
	Nidec (Zhejiang)		1,044		—		—		98			1,142
	Nidec Sankyo		27,312		2,114		—		107			29,533
	Nidec Copal		16,462		—		—		—			16,462
	Nidec Tosok		1,038		—		—		—			1,038
	Nidec Copal Electronics		6,561		—		—		—			6,561
	Nidec Techno Motor		2,049		—		—		—			2,049
	Nidec Motor		55,008		—		—		8,070			63,078
	Nidec Motors & Actuators		6,385		—		—		933			7,318
	All Others		9,922		9,668		—		511			20,101
		¥	132,775	¥	11,782	¥	—	¥	10,370		¥	154,927
Schedule of Finite-Lived Intangible Assets by Major Class	'
	Intangible assets subject to amortization are summarized as follows:
		Yen in millions
		March 31
		2013						2014
		Gross		Accumulated		Carrying		Gross			Accumulated		Carrying
		carrying		amortization		amounts		carrying			amortization		amounts
		amounts						amounts
	Proprietary technology	¥	10,017	¥	1,469	¥	8,548	¥	11,671		¥	2,535	¥	9,136
	Customer relationships		43,305		5,817		37,488		48,157			9,626		38,531
	Software		13,830		6,878		6,952		18,001			8,625		9,376
	Other		5,718		1,925		3,793		6,988			3,345		3,643
	Total	¥	72,870	¥	16,089	¥	56,781	¥	84,817		¥	24,131	¥	60,686
Schedule of Expected Amortization Expense	'
	The estimated aggregate amortization expense for intangible assets for the next five years is as follows:
	Years ending March 31,	Yen in millions
	2015	¥	6,773
	2016		6,445
	2017		5,767
	2018		5,123
	2019		4,656
Series of Individually Immaterial Business Acquisitions	'
Goodwill Allocated to Operating Segment	'
	Operating Segment	Yen in millions
		Amount of Goodwill		Amount of Goodwill
				deductible for tax
				purposes
	Nidec Sankyo	¥	2,114	¥	334
	All Others		9,668		393
	Total	¥	11,782	¥	727

Supplemental_cash_flow_informa1

Supplemental cash flow information (Tables)	12 Months Ended
	Mar. 31, 2014
Schedule of Cash Flow, Supplemental Disclosures	'
	The supplemental information associated with the consolidated statements of cash flows for the years ended March 31, 2012, 2013 and 2014 are as follows:
		Yen in millions
		For the year  ended
		March 31
		2012		2013		2014
	Cash paid during the fiscal year for:
	Income taxes	¥	8,197	¥	25,879	¥	12,613
	Interest		327		395		1,636
	Non-cash investing and financing activities:
	Capital leasing receivables		31		—		—
	Capital lease obligations		214		206		499
	Change in ownership of subsidiaries in connection with share exchange transaction
	—Change in common stock		—		3,270		4,279
	—Change in treasury stock		—		16,710		20,655

Allowance_for_doubtful_account1

Allowance for doubtful accounts (Tables)	12 Months Ended
	Mar. 31, 2014
Allowance for Doubtful Accounts	'
	An analysis of activity within the allowance for doubtful accounts for the years ended March 31, 2012, 2013 and 2014 are as follows:
		Yen in millions
		2012			2013			2014
	Allowance for doubtful accounts at beginning of the year	¥	1,013		¥	1,002		¥	1,375
	Provision for doubtful accounts, net of reversal		30			166			366
	Write-offs		(30	)		(90	)		(267	)
	Translation adjustment and other		(11	)		297			119
	Allowance for doubtful accounts at the end of the year	¥	1,002		¥	1,375		¥	1,593

Inventories_Tables

Inventories (Tables)	12 Months Ended
	Mar. 31, 2014
Schedule of Inventory, Current	'
	Inventories consist of the following:
		Yen in millions
		March 31
		2013		2014
	Finished goods	¥	42,599	¥	51,293
	Raw materials		30,839		39,993
	Work in process		23,526		28,926
	Supplies and other		2,862		3,669
		¥	99,826	¥	123,881

Other_current_assets_Tables

Other current assets (Tables)	12 Months Ended
	Mar. 31, 2014
Schedule Of Prepaid Expenses and Other Current Assets	'
	Other current assets as of March 31, 2013 and 2014 consist of the following:
		Yen in millions
		March 31
		2013		2014
	Other receivable	¥	13,740	¥	13,906
	Deferred tax assets (Note 16)		12,787		10,434
	Costs on uncompleted construction contracts		5,799		9,572
	Prepaid expenses		4,079		5,225
	Other		11,954		8,926
		¥	48,359	¥	48,063

Marketable_securities_and_othe1

Marketable securities and other securities investments (Tables)	12 Months Ended
	Mar. 31, 2014
Investments in Debt and Marketable Equity Securities and Certain Trading Assets Disclosure	'
	Marketable securities and other securities investments include debt and equity securities of which the aggregate fair value, gross unrealized gains and losses and cost are as follows:
		Yen in millions
		March 31, 2013
		Cost		Gross		Gross		Fair
				unrealized		unrealized		value
				gains		losses
	Available-for-sale
	Equity securities	¥	7,838	¥	5,814	¥	3	¥	13,649
	Debt securities		405		11		5		411
	Held-to-maturity
	Japanese government debt securities		301		3		—		304
		¥	8,544	¥	5,828	¥	8	¥	14,364
	Securities not practicable to estimate fair value
	Equity securities	¥	1,539
		Yen in millions
		March 31, 2014
		Cost		Gross		Gross		Fair
				unrealized		unrealized		value
				gains		losses
	Available-for-sale
	Equity securities	¥	7,652	¥	6,731	¥	0	¥	14,383
	Debt securities		—		—		—		—
	Held-to-maturity
	Japanese government debt securities		400		2		—		402
		¥	8,052	¥	6,733	¥	0	¥	14,785
	Securities not practicable to estimate fair value
	Equity securities	¥	1,654
Unrealized Loss Position Investments	'
	The following tables present the gross unrealized losses on, and fair value of, NIDEC’s investment securities, aggregated by investment category and length of time that individual investment securities have been in a continuous unrealized loss position.
		Yen in millions
		March 31, 2013
		Less than 12 months				12 months or more
		Fair value		Unrealized		Fair value		Unrealized
				loss				loss
	Equity securities	¥	16	¥	1	¥	23	¥	2
	Debt securities		182		5		—		—
		¥	198	¥	6	¥	23	¥	2
		Yen in millions
		March 31, 2014
		Less than 12 months				12 months or more
		Fair value		Unrealized		Fair value		Unrealized
				loss				loss
	Equity securities	¥	0	¥	0	¥	1	¥	0
	Debt securities		—		—		—		—
		¥	0	¥	0	¥	1	¥	0

Other_noncurrent_assets_Tables

Other non-current assets (Tables)	12 Months Ended
	Mar. 31, 2014
Schedule of Other Assets, Noncurrent	'
	Other non-current assets as of March 31, 2013 and 2014 consist of the following:
			Yen in millions
			March 31
			2013		2014
	Intangible assets *1		¥	63,989	¥	68,606
	Deferred tax assets			7,116		1,482
	Other *2			5,810		7,599
			¥	76,915	¥	77,687
	Notes:
	*1	“Intangible assets” information is described in Note 4 “Goodwill and other intangible assets”
	*2	“Other” primarily consists of Long-term prepaid expenses.

Shortterm_borrowings_and_longt1

Short-term borrowings and long-term debt (Tables)	12 Months Ended
	Mar. 31, 2014
Schedule of Short-term Debt	'
	Short-term borrowings at March 31, 2013 and 2014 consist of the following:
		Yen in millions
		March 31
		2013			2014
	Loans, principally from banks with average interest at March 31, 2013 and 2014 of 0.21% and 0.31% per annum, respectively	¥	32,798		¥	22,600
		¥	32,798		¥	22,600
Schedule of Long-term Debt Instruments	'
	Long-term debt at March 31, 2013 and 2014 are comprised of the following:
		Yen in millions
		March 31
		2013			2014
	Unsecured loans, representing obligations principally to banks and an insurance company
	Due 2013 to 2026 in 2013 with interest ranging from 0.00% to 6.40% per annum in 2013	¥	73,925			—
	Due 2014 to 2026 in 2014 with interest ranging from 0.00% to 6.80% per annum in 2014		—		¥	77,804
	Zero coupon convertible bonds due 2015		100,247			95,891
	Convertible at ¥5,313 for one common share
	Unsecured straight bonds due 2017		65,000			65,000
	Interest at 0.39% per annum in 2013 and 2014
	Unsecured straight bonds due 2019		15,000			15,000
	Interest at 0.60% per annum in 2013 and 2014
	Unsecured straight bonds due 2022		20,000			20,000
	Interest at 0.96% per annum in 2013 and 2014
	Unsecured straight bonds due 2016		—			50,000
	Interest at 0.21% per annum in 2014
	Unsecured straight bonds due 2014		100			100
	Issued by subsidiaries in 2011 which was newly consolidated in 2013
	Interest at 0.72% per annum in 2013 and 2014
	Capital lease obligations
	Due 2013 to 2019 in 2013, with interest from 0.00% to 8.27% per annum in 2013		5,627			—
	Due 2014 to 2019 in 2014, with interest from 0.00% to 15.74% per annum in 2014		—			4,861
			279,899			328,656
	Less—Bonds current portion due within one year		(100,247	)		(100	)
	Less—Long-term debt current portion due within one year		(31,841	)		(27,478	)
	Less—Capital lease obligation current portion due within one year		(1,540	)		(1,667	)
		¥	146,271		¥	299,411
Schedule of Maturities of Long-term Debt	'
	The aggregate amounts of annual maturity of long-term debt during the next five years are as follows:
		Yen in millions
		Year ending
		March 31
	2015	¥	29,245
	2016		116,841
	2017		81,153
	2018		66,167
	2019		137
	2020 and thereafter	¥	35,113
Yen Denominated zero coupon convertible bonds due 2015	'
Schedule of Long-term Debt Instruments	'
	Detail of Zero coupon convertible bonds, due 2015 is as follow;
		Yen in millions
		March 31
		2013			2014
	Principal amount	¥	100,000		¥	95,750
	Unamortized premium		247			141
	Total	¥	100,247		¥	95,891

Other_current_liabilities_Tabl

Other current liabilities (Tables)	12 Months Ended
	Mar. 31, 2014
Other Current Liabilities	'
	Other current liabilities as of March 31, 2013 and 2014 consist of the following:
		Yen in millions
		March 31
		2013		2014
	Accounts payable for property, plant and equipment	¥	10,354	¥	9,857
	Advances received		6,437		7,152
	Income taxes payable		4,013		4,557
	Other		11,628		11,576
		¥	32,432	¥	33,142

Pension_and_severance_plans_Ta

Pension and severance plans (Tables)	12 Months Ended
	Mar. 31, 2014
Schedule of Amounts Recognized in Balance Sheet	'
	Amounts included in the consolidated balance sheet are comprised of:
			Yen in millions
			March 31
			2013			2014
	Accrued pension and severance costs		¥	6,272		¥	6,045
	Other non-current assets			(20	)		(74	)
	Net amounts recognized		¥	6,252		¥	5,971
Schedule of Allocation of Plan Assets	'
	The fair values of NIDEC’s pension plan assets at March 31, 2013 and 2014, by asset category, are as follows:
			Yen in millions
			Fair Value  at			Fair Value Measurements
			March 31, 2013			Using Inputs Considered as
						Level 1			Level 2			Level 3
	Equity securities:
	Japanese companies		¥	302		¥	302		¥	—		¥	—
	Foreign companies			302			302			—			—
	Debt securities:
	Pooled funds *1			593			—			593			—
	Other assets:
	Cash and cash equivalents			1,103			1,103			—			—
	Life insurance company general accounts			3,040			—			3,040			—
	Pooled funds *2			7,431			—			7,431			—
	Others			2,070			—			—			2,070
	Total		¥	14,841		¥	1,707		¥	11,064		¥	2,070
	*1	These funds invest in approximately 86% Japanese bonds, 14% foreign bonds.
	*2	These funds primarily invest in listed equity securities consisting of approximately 12% Japanese companies and 60% foreign companies, and debt security consisting of approximately 9% Japanese bonds and 16% foreign bonds.
			Yen in millions
			Fair Value  at			Fair Value Measurements
			March 31, 2014			Using Inputs Considered as
						Level 1			Level 2			Level 3
	Equity securities:
	Japanese companies		¥	281		¥	281		¥	—		¥	—
	Foreign companies			233			233			—			—
	Debt securities:
	Pooled funds *1			757			—			757			—
	Other assets:
	Cash and cash equivalents			1,793			1,793			—			—
	Life insurance company general accounts			4,833			—			4,833			—
	Pooled funds *2			11,183			—			11,183			—
	Others			2,464			—			2,464			—
	Total		¥	21,544		¥	2,307		¥	19,237		¥	—
	*1	These funds invest in approximately 68% Japanese bonds, 32% foreign bonds.
	*2	These funds primarily invest in listed equity securities consisting of approximately 7% Japanese companies and 31% foreign companies, and debt security consisting of approximately 6% Japanese bonds and 37% foreign bonds.
Changes in Fair Value of Plan Assets Categorized as Level Three	'
	The table below sets forth a summary of changes in the fair value of plan assets categorized as Level 3 for the years ended March 31, 2013 and 2014.
	Others		Yen in millions
			March 31			March 31
			2013			2014
	Balance at beginning of year		¥	—		¥	2,070
	Acquisition *1			1,159			—
	Purchases			582			—
	Actual return on plan assets and other			329			394
	Transfers out of level 3 *2			—			(2,464	)
	Balance at end of year		¥	2,070		¥	—
	*1	As a result of the Acquisition of Minster, NIDEC acquired the plan assets categorized as Level 3.
	*2	All the level 3 assets were transferred into level 2 because we got the ability to redeem the level 3 assets at net asset value at the measurement date.
Schedule of Expected Benefit Payments	'
	The future benefit payments for defined benefit plans are expected as follows:
			Yen in millions
			Japanese			Foreign
			plans			plans
	2015		¥	811		¥	1,030
	2016			932			1,043
	2017			886			942
	2018			892			1,122
	2019			1,153			1,121
	Years 2020-2024		¥	5,667		¥	5,709
Japanese plans	'
Schedule of Net Funded Status	'
	Information regarding NIDEC’s employees’ defined benefit plans is as follows:
	Japanese plans:
			Yen in millions
			March 31
			2013			2014
	Change in benefit obligation:
	Benefit obligation at beginning of year		¥	14,255		¥	14,079
	Service cost			910			927
	Interest cost			197			180
	Actuarial loss			163			196
	Acquisition and other			26			4,014
	Plan amendment			—			(143	)
	Benefits paid			(1,472	)		(1,851	)
				14,079			17,402
	Change in plan assets:
	Fair value of plan assets at beginning of year			7,096			7,827
	Actual return on plan assets			823			576
	Employer contribution			622			1,135
	Acquisition and other			—			2,856
	Benefits paid			(714	)		(963	)
	Fair value of plan assets at end of year			7,827			11,431
	Funded status		¥	(6,252	)	¥	(5,971	)
Schedule of Net Periodic Benefit Cost Not yet Recognized	'
	Amounts included in accumulated other comprehensive income (loss) as pension liability adjustments are comprised of:
			Yen in millions
			March 31
			2013			2014
	Actuarial loss		¥	(1,741	)	¥	(1,562	)
	Prior service credit			1,407			1,393
	Pension liability adjustments, pre-tax		¥	(334	)	¥	(169	)
Schedule of Accumulated Benefit Obligations in Excess of Fair Value of Plan Assets	'
	The projected benefit obligation, accumulated benefit obligation and fair value of plan assets for which the accumulated benefit obligations exceed plan assets are as follows:
			Yen in millions
			March 31
			2013			2014
	Projected benefit obligations		¥	13,924		¥	12,805
	Accumulated benefit obligations			13,718			12,539
	Fair value of plan assets		¥	7,653		¥	6,725
Schedule of Net Benefit Costs	'
			Yen in millions
			For the year  ended
			March 31
			2012			2013			2014
	Components of net periodic (benefit) cost:
	Service cost		¥	983		¥	910		¥	927
	Interest cost			213			197			180
	Expected return on plan assets			(134	)		(139	)		(164	)
	Amortization of net actuarial loss			120			123			92
	Amortization of prior service credit			(171	)		(146	)		(157	)
	Losses from curtailments and settlements			296			—			—
	Net periodic pension cost		¥	1,307		¥	945		¥	878
Japanese plans | Benefit Obligations	'
Schedule of Assumptions Used	'
	Weighted-average assumptions used to determine benefit obligations as of March 31, 2013 and 2014 are as follows:
			March 31
			2013			2014
	Discount rate			1.3	%		1.2	%
	Rate of compensation increase			2.2	%		4.2	%
Japanese plans | Net Periodic Benefit Cost	'
Schedule of Assumptions Used	'
	Weighted-average assumptions used to determine net pension and severance costs for the years ended March 31, 2012, 2013 and 2014 are as follows:
			For the year ended
			March 31
			2012			2013			2014
	Discount rate			1.6	%		1.6	%		1.3	%
	Expected return on plan assets			2.3	%		2.3	%		2.6	%
	Rate of compensation increase			2.2	%		2.3	%		2.2	%
Foreign plans	'
Schedule of Net Funded Status	'
			Yen in millions
			March 31
			2013			2014
	Change in benefit obligation:
	Benefit obligation at beginning of year		¥	6,119		¥	19,966
	Service cost			549			553
	Interest cost			625			741
	Actuarial loss (gain)			992			(548	)
	Acquisition and other			10,171			131
	Foreign currency exchange rate changes			2,297			2,155
	Benefits paid			(787	)		(1,032	)
				19,966			21,966
	Change in plan assets:
	Fair value of plan assets at beginning of year			563			7,014
	Actual return on plan assets			505			957
	Employer contribution			588			2,103
	Acquisition and other			4,994			—
	Foreign currency exchange rate changes			886			714
	Benefits paid			(522	)		(675	)
	Fair value of plan assets at end of year			7,014			10,113
	Funded status		¥	(12,952	)	¥	(11,853	)
Schedule of Amounts Recognized in Balance Sheet	'
	Amounts included in the consolidated balance sheet are comprised of:
			Yen in millions
			March 31
			2013			2014
	Accrued pension and severance costs		¥	12,952		¥	11,853
	Net amounts recognized		¥	12,952		¥	11,853
Schedule of Net Periodic Benefit Cost Not yet Recognized	'
	Amounts included in accumulated other comprehensive income (loss) as pension liability adjustments are comprised of:
			Yen in millions
			March 31
			2013			2014
	Actuarial loss		¥	(952	)	¥	142
	Pension liability adjustments, pre-tax		¥	(952	)	¥	142
Schedule of Accumulated Benefit Obligations in Excess of Fair Value of Plan Assets	'
	The projected benefit obligations, accumulated benefit obligations and fair value of plan assets for which the accumulated benefit obligations exceed plan assets are as follows:
			Yen in millions
			March 31
			2013			2014
	Projected benefit obligations		¥	19,966		¥	21,498
	Accumulated benefit obligations			19,708			21,300
	Fair value of plan assets		¥	7,014		¥	9,464
Schedule of Net Benefit Costs	'
			Yen in millions
			For the year  ended
			March 31
			2012			2013			2014
	Components of net periodic (benefit) cost:
	Service cost		¥	441		¥	549		¥	553
	Interest cost			230			625			741
	Expected return on plan assets			(48	)		(445	)		(443	)
	Amortization of net actuarial loss (gain)			(2	)		6			27
	Net periodic pension cost		¥	621		¥	735		¥	878
Foreign plans | Benefit Obligations	'
Schedule of Assumptions Used	'
	Weighted-average assumptions used to determine benefit obligations as of March 31, 2013 and 2014 are as follows:
			March 31
			2013			2014
	Discount rate			4.4	%		4.4	%
	Rate of compensation increase			3	%		3	%
Foreign plans | Net Periodic Benefit Cost	'
Schedule of Assumptions Used	'
	Weighted-average assumptions used to determine net pension and severance costs for the years ended March 31, 2012, 2013 and 2014 are as follows:
			For the year ended
			March 31
			2012			2013			2014
	Discount rate			5.7	%		4.7	%		4.4	%
	Expected return on plan assets			4.4	%		7.5	%		7.5	%
	Rate of compensation increase			2.9	%		3	%		3	%

Other_longterm_liabilities_Tab

Other long-term liabilities (Tables)	12 Months Ended
	Mar. 31, 2014
Other Noncurrent Liabilities	'
	Other long-term liabilities as of March 31, 2013 and 2014 consist of the following:
			Yen in millions
			March 31
			2013		2014
	Deferred tax liabilities		¥	14,715	¥	17,138
	Unrecognized tax benefits, accrued interest and penalty*			2,173		2,321
	Other			4,329		5,785
			¥	21,217	¥	25,244
	* Note:	“Unrecognized tax benefits, accrued interest and penalty” information is described in Note 16 “Income taxes”

Equity_Tables

Equity (Tables)	12 Months Ended
	Mar. 31, 2014
Changes in Accumulated Other Comprehensive Income (Loss) by Component	'
	The changes in accumulated other comprehensive income (loss) by component are as follows:
			Yen in Millions
			Foreign			Unrealized			Unrealized			Pension			Total
			currency			gains			gains			liability
			translation			(losses)			(losses)			adjustments
			adjustments			from			from
						securities			derivative
									instruments
	For the year ended March 31, 2014:
	Balance at March 31, 2013			12,636			1,187			242			(1,112	)		12,953
	Other comprehensive income (loss) before reclassifications			41,903			3,145			(244	)		754			45,558
	Amounts reclassified from accumulated other comprehensive income (loss)			—			(147	)		(22	)		34			(135	)
	Net change during the current period other comprehensive income (loss)			41,903			2,998			(266	)		788			45,423
	Balance at March 31, 2014			54,539			4,185			(24	)		(324	)		58,376
Reclassification Out of Accumulated Other Comprehensive Income (Loss)	'
	Reclassification out of accumulated other comprehensive income (loss) are as follows:
			Yen in Millions
			Amount			Affected line items
			Reclassified			in consolidated statement of income
			from
			Accumulated
			other
			comprehensive
			income (loss) *1
	For the year ended March 31, 2014:
	Unrealized gains (losses) from securities			(230	)	Gain from marketable securities, net
				83		Income taxes
				(147	)	Consolidated net income
				—		Net income attributable to noncontrolling interests
				(147	)	Net income attributable to Nidec Corporation
	Unrealized gains (losses) from derivative instruments			(37	)	Cost of products sold, Interest expense.
				15		Income taxes
				(22	)	Consolidated net income
				—		Net income attributable to noncontrolling interests
				(22	)	Net income attributable to Nidec Corporation
	Pension liability adjustments			(38	)	*2
				22		Income taxes
				(16	)	Consolidated net income
				50		Net income attributable to noncontrolling interests
				34		Net income attributable to Nidec Corporation
	Total amount reclassified, net of tax and noncontrolling interests			(135	)
	*1	Amounts in parentheses indicate gains in consolidated statement of income.
	*2	This accumulated other comprehensive income (loss) component is included in the computation of net periodic pension cost.
Schedule of Comprehensive Income (Loss)	'
	Tax effects allocated to each component of other comprehensive income (loss) and reclassification adjustments, including amounts attributable to noncontrolling interests for the years ended March 31, 2012, 2013 and 2014 are as follows:
			Yen in millions
			Pre-tax			Tax  benefit/			Net-of-tax
			amount			(expense)			amount
	For the year ended March 31, 2012:
	Foreign currency translation adjustments:
	Foreign currency translation adjustments arising during period		¥	(2,665	)	¥	—		¥	(2,665	)
	Reclassification adjustments for gains and losses realized in net income			105			—			105
	Unrealized gains (losses) from securities:
	Unrealized holding losses arising during period			(358	)		129			(229	)
	Reclassification adjustments for gains and losses realized in net income			253			(31	)		222
	Unrealized gains (losses) from derivative instruments qualifying for cash flow hedges:
	Unrealized losses arising during period			(541	)		216			(325	)
	Reclassification adjustments for gains and losses realized in net income			291			(112	)		179
	Pension liability adjustment:
	Actuarial losses arising during period			(831	)		114			(717	)
	Prior service cost arising during period			(10	)		4			(6	)
	Reclassification adjustments for actuarial gains and losses realized in net income			891			(340	)		551
	Reclassification adjustments for prior service credit and cost realized in net income			463			(198	)		265
	Other comprehensive income (loss)		¥	(2,402	)	¥	(218	)	¥	(2,620	)
	For the year ended March 31, 2013:
	Foreign currency translation adjustments:
	Foreign currency translation adjustments arising during period		¥	62,024		¥	—		¥	62,024
	Reclassification adjustments for gains and losses realized in net income			134			—			134
	Unrealized gains (losses) from securities:
	Unrealized holding gains arising during period			156			(56	)		100
	Reclassification adjustments for gains and losses realized in net income			88			(37	)		51
	Unrealized gains (losses) from derivative instruments qualifying for cash flow hedges:
	Unrealized gains arising during period			93			(30	)		63
	Reclassification adjustments for gains and losses realized in net income			196			(90	)		106
	Pension liability adjustment:
	Actuarial losses arising during period			(328	)		(93	)		(421	)
	Prior service cost arising during period			—			—			—
	Reclassification adjustments for actuarial gains and losses realized in net income			130			(45	)		85
	Reclassification adjustments for prior service credit and cost realized in net income			(152	)		55			(97	)
	Other comprehensive income (loss)		¥	62,341		¥	(296	)	¥	62,045
	For the year ended March 31, 2014:
	Foreign currency translation adjustments:
	Foreign currency translation adjustments arising during period		¥	43,429		¥	—		¥	43,429
	Reclassification adjustments for gains and losses realized in net income			—			—			—
	Unrealized gains (losses) from securities:
	Unrealized holding gains arising during period			4,567			(1,440	)		3,127
	Reclassification adjustments for gains and losses realized in net income			(230	)		83			(147	)
	Unrealized gains (losses) from derivative instruments qualifying for cash flow hedges:
	Unrealized losses arising during period			(397	)		153			(244	)
	Reclassification adjustments for gains and losses realized in net income			(37	)		15			(22	)
	Pension liability adjustment:
	Actuarial gains arising during period			1,071			(378	)		693
	Prior service cost arising during period			74			(14	)		60
	Reclassification adjustments for actuarial gains and losses realized in net income			119			(35	)		84
	Reclassification adjustments for prior service credit and cost realized in net income			(157	)		57			(100	)
	Other comprehensive income (loss)		¥	48,439		¥	(1,559	)	¥	46,880

Income_taxes_Tables

Income taxes (Tables)	12 Months Ended
	Mar. 31, 2014
Schedule of Income before Income Tax, Domestic and Foreign	'
	The components of income from continuing operations before income tax comprise the following:
		Yen in millions
		For the year ended
		March 31
		2012			2013			2014
	Income (loss) from continuing operations before income taxes:
	The Company and domestic subsidiaries	¥	46,181		¥	(7,473	)	¥	25,463
	Foreign subsidiaries		24,675			20,871			59,201
		¥	70,856		¥	13,398		¥	84,664
Schedule of Components of Income Tax Expense (Benefit)	'
	The provision for income taxes consists of the following:
		Yen in millions
		For the year ended
		March 31
		2012			2013			2014
	Current income tax expense/(benefit):
	The Company and domestic subsidiaries	¥	(4,462	)	¥	9,200		¥	1,872
	Foreign subsidiaries		6,694			5,713			10,139
	Total current		2,232			14,913			12,011
	Deferred income tax expense (benefit):
	The Company and domestic subsidiaries		16,289			(5,504	)		12,649
	Foreign subsidiaries		280			(2,847	)		1,069
	Total deferred		16,569			(8,351	)		13,718
	Total provision	¥	18,801		¥	6,562		¥	25,729
Schedule of Effective Income Tax Rate Reconciliation	'
	Reconciliation of the differences between the statutory tax rate and the effective income tax rate is as follows:
		For the year ended
		March 31
		2012			2013			2014
	Statutory tax rate		41	%		38	%		38	%
	Increase (reduction) in taxes resulting from:
	Tax benefit in foreign subsidiaries		(16.1	)		(43.6	)		(14.6	)
	Tax on undistributed earnings		5.1			8.9			2.2
	Valuation allowance		4.1			33.7			(2.3	)
	Liabilities for unrecognized tax benefits		(10.5	)		2.3			(0.1	)
	Reversal of deferred tax assets related to foreign tax credit		—			—			5.3
	Changes in Japanese income tax rates		1.4			—			0.3
	Other		1.5			9.7			1.6
	Effective income tax rate		26.5	%		49	%		30.4	%
Summary of Income Tax Holiday	'
	The aggregate amounts and per share effects of tax holidays are as follows:
		Yen in millions
		For the year ended
		March 31
		2012			2013			2014
	Aggregate amounts of tax holidays	¥	4,023		¥	2,968		¥	4,362
		Yen
	Per share—basic	¥	14.63		¥	11.02		¥	16.03
	—diluted	¥	13.69		¥	10.3		¥	15.02
Schedule of Deferred Tax Assets and Liabilities	'
	The significant components of deferred tax assets and liabilities are as follows:
		Yen in millions
		March 31
		2013			2014
	Deferred tax assets:
	Inventories	¥	3,142		¥	2,818
	Marketable securities		1,102			—
	Property, plant and equipment		—			5,019
	Accrued bonus		2,242			2,330
	Accrued enterprise tax		—			221
	Pension and severance plans		4,526			4,464
	Operating loss carryforwards for tax purposes		13,646			12,811
	Foreign tax credit		5,402			—
	Accrued vacation		1,135			1,090
	Accrued expenses		3,636			1,421
	Other		2,613			2,666
	Gross deferred tax assets		37,444			32,840
	Less—Valuation allowance		(14,492	)		(14,561	)
	Net deferred tax assets		22,952			18,279
	Deferred tax liabilities:
	Refund of enterprise taxes		(285	)		—
	Basis difference of acquired assets		(4,495	)		(458	)
	Property, plant and equipment		(1,058	)		—
	Undistributed earnings not permanently reinvested		(7,856	)		(9,311	)
	Marketable securities		—			(321	)
	Intangible assets		(4,816	)		(9,813	)
	Other		(1,083	)		(5,181	)
	Gross deferred tax liabilities		(19,593	)		(25,084	)
	Net deferred tax assets (liabilities)	¥	3,359		¥	(6,805	)
Summary of Valuation Allowance	'
	The net changes in the total valuation allowance for deferred tax assets for the years ended March 31, 2012, 2013 and 2014 consist of the following:
		Yen in millions
		March 31
		2012			2013			2014
	Valuation allowance at beginning of year	¥	(6,235	)	¥	(9,786	)	¥	(14,492	)
	Additions		(3,490	)		(7,660	)		(4,231	)
	Deductions		1,581			2,994			4,183
	Impact on newly acquired companies		(1,642	)		(40	)		(21	)
	Valuation allowance at end of year	¥	(9,786	)	¥	(14,492	)	¥	(14,561	)
Components of net deferred tax assets	'
	Net deferred tax assets are included in the consolidated balance sheets as follows:
		Yen in millions
		March 31
		2013			2014
	Deferred tax assets:
	Other current assets	¥	12,787		¥	10,434
	Other non-current assets		7,116			1,482
	Deferred tax liabilities:
	Other current liabilities		(1,829	)		(1,583	)
	Other long-term liabilities		(14,715	)		(17,138	)
	Net deferred tax assets	¥	3,359		¥	(6,805	)
Reconciliation of the Beginning and Ending Amounts of Unrecognized Tax Benefits	'
	A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows:
		Yen in millions
		For the year ended
		March 31,
		2012			2013			2014
	Balance at April 1	¥	9,199		¥	1,766		¥	2,361
	Additions for tax positions of the current year		1,766			44			357
	Additions for tax positions of prior years		—			551			—
	Reduction for tax positions of prior years		—			—			(486	)
	Settlements		(9,199	)		—			—
	Balance at March 31	¥	1,766		¥	2,361		¥	2,232

Reconciliation_of_the_differen1

Reconciliation of the differences between basic and diluted earnings per share (Tables)	12 Months Ended
	Mar. 31, 2014
Schedule of Earnings Per Share Reconciliation	'
	The tables below set forth a reconciliation of the differences between basic and diluted income attributable to Nidec Corporation per share for the years ended March 31, 2012, 2013 and 2014.
		Yen in			Thousands of		Yen
		millions			shares
		Net income			Weighted-		Net income
		(loss)			average		(loss)
		attributable to			shares		attributable to
		Nidec					Nidec
		Corporation					Corporation
							per share
	For the year ended March 31, 2012:
	Basic net income attributable to Nidec Corporation per share:
	Income from continuing operations attributable to Nidec Corporation	¥	46,242			274,981	¥	168.16
	Loss on discontinued operations attributable to Nidec Corporation		(5,511	)		274,981		(20.04	)
	Net income attributable to Nidec Corporation		40,731			274,981		148.12
	Effect of dilutive securities:
	Zero coupon convertible bonds		(55	)		18,821
	Diluted net income attributable to Nidec Corporation per share:
	Income from continuing operations attributable to Nidec Corporation		46,187			293,802		157.2
	Loss on discontinued operations attributable to Nidec Corporation		(5,511	)		293,802		(18.75	)
	Net income attributable to Nidec Corporation	¥	40,676			293,802	¥	138.45
	For the year ended March 31, 2013:
	Basic net income attributable to Nidec Corporation per share:
	Net income attributable to Nidec Corporation	¥	7,986			269,429	¥	29.64
	Effect of dilutive securities:
	Zero coupon convertible bonds		(61	)		18,821
	Diluted net income attributable to Nidec Corporation per share:
	Net income attributable to Nidec Corporation	¥	7,925			288,250	¥	27.49
		Yen in			Thousands of		Yen
		millions			shares
		Net income			Weighted-		Net income
		(loss)			average		(loss)
		attributable to			shares		attributable to
		Nidec					Nidec
		Corporation					Corporation
							per share
	For the year ended March 31, 2014:
	Basic net income attributable to Nidec Corporation per share:
	Net income attributable to Nidec Corporation	¥	56,404			272,078	¥	207.31
	Effect of dilutive securities:
	Zero coupon convertible bonds		(64	)		18,400
	Diluted net income attributable to Nidec Corporation per share:
	Net income attributable to Nidec Corporation	¥	56,340			290,478	¥	193.96

Derivatives_Tables

Derivatives (Tables)	12 Months Ended
	Mar. 31, 2014
Schedule of Derivative Instruments	'
	Derivatives designated as hedging instruments are as follows:
		Yen in millions
		March 31, 2013				March 31, 2014
	Foreign exchange forward contracts	¥	7,403			¥	9,736
	Interest rate swap agreements		32,205				20,587
	Commodity futures		3,739				4,610
	Derivatives not designated as hedging instruments are as follows:
		Yen in millions
		March 31, 2013				March 31, 2014
	Foreign exchange forward contracts	¥	149			¥	1,800
	Currency option contracts		231				53
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value	'
	Derivatives designated as cash flow hedge are as follows:
				Asset Derivatives
		Balance sheet location		Yen in millions
				March 31,				March 31,
				2013				2014
	Foreign exchange forward contracts	Other current assets		¥	659			¥	271
				Liability Derivatives
		Balance sheet location		Yen in millions
				March 31,				March 31,
				2013				2014
	Foreign exchange forward contracts	Other current liabilities		¥	22			¥	1
	Interest rate swap agreements	Other current liabilities			20				31
	Commodity futures	Other current liabilities			181				239
	Derivatives not designated as hedging instruments are as follows:
				Asset Derivatives
		Balance sheet location		Yen in millions
				March 31,				March 31,
				2013				2014
	Foreign exchange forward contracts	Other current assets		¥	16			¥	4
	Currency option contracts	Other current assets			10				7
Schedule of Derivative Instruments, Gain (Loss) in Statement of Financial Performance	'
	Derivatives designated as cash flow hedge are as follows:
	Gains (losses) recognized in accumulated other comprehensive income
		Yen in millions
		For the year ended March 31
		2012				2013				2014
	Foreign exchange forward contracts	¥	(68	)		¥	277			¥	(229	)
	Interest rate swap agreements		—				(6	)			(5	)
	Commodity futures		(78	)			(102	)			(32	)
	Gains (losses) reclassified from accumulated other comprehensive income into income (effective portion)
		Statement of income location		Yen in millions
				For the year ended March 31
				2012				2013				2014
	Foreign exchange forward contracts	Cost of sales		¥	17			¥	81			¥	241
	Interest rate swap agreements	Interest expense			—				(4	)			(7	)
	Commodity futures	Cost of sales			(196	)			(183	)			(212	)
	Derivatives not designated as hedging instruments are as follows:
	Gains (losses) recognized in income
		Statement of income location		Yen in millions
				For the year ended March 31
				2012				2013				2014
	Foreign exchange forward contracts	Foreign exchange gain (loss), net		¥	—			¥	22			¥	23
	Currency option contracts	Foreign exchange gain (loss), net			—				40				18
	Interest rate currency swap agreements	Other, net			2				—				—

Fair_Value_Tables

Fair Value (Tables)	12 Months Ended
	Mar. 31, 2014
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	'
	The following table provides information by level for assets and liabilities that are measured at fair value, as defined by ASC 820, on a recurring basis.
		Yen in millions
		Fair Value  at			Fair Value Measurements
		March 31, 2013			Using Inputs Considered as
					Level 1			Level 2			Level 3
	Assets:
	Marketable securities	¥	14,060		¥	13,649		¥	411			—
	Derivatives		685			—			685			—
	Total assets:	¥	14,745		¥	13,649		¥	1,096			—
	Liabilities:
	Derivatives	¥	223		¥	181		¥	42			—
		Yen in millions
		Fair Value  at			Fair Value Measurements
		March 31, 2014			Using Inputs Considered as
					Level 1			Level 2			Level 3
	Assets:
	Marketable securities	¥	14,383		¥	14,383			—			—
	Derivatives		282			—			282			—
	Total assets:	¥	14,665		¥	14,383		¥	282			—
	Liabilities:
	Derivatives	¥	271		¥	239		¥	32			—
Fair Value, by Balance Sheet Grouping	'
	The carrying amount and estimated fair values of NIDEC’s financial instruments, excluding those disclosed elsewhere, are summarized as follows:
		Yen in millions						Yen in millions
		March 31, 2013						March 31, 2014
		Carrying			Estimated			Carrying			Estimated
		amount			fair value			amount			Fair value
	Asset (Liability):
	Cash and cash equivalents	¥	193,420		¥	193,420		¥	247,740		¥	247,740
	Short-term investments		1,552			1,552			2,344			2,344
	Long-term investments		—			—			83			82
	Short-term loan receivable		132			132			157			157
	Long-term loan receivable		89			91			48			50
	Short-term borrowings		(32,798	)		(32,798	)		(22,600	)		(22,600	)
	Long-term debt including the current portion and excluding capital lease obligation and bonds		(73,925	)		(73,907	)		(77,804	)		(77,486	)
	Bonds including the current portion	¥	(200,347	)	¥	(200,850	)	¥	(245,991	)	¥	(271,853	)

Lease_commitments_Tables

Lease commitments (Tables)	12 Months Ended
	Mar. 31, 2014
Schedule of Capital Leased Assets	'
	An analysis of leased assets under capital leases is as follows:
		Yen in millions
		March 31
	Class of property	2013			2014
	Machinery and equipment	¥	6,950		¥	7,336
	Other leased assets		65			109
	Less—Accumulated amortization		(1,345	)		(2,511	)
		¥	5,670		¥	4,934
Schedule of Future Minimum Lease Payments for Capital Leases	'
	The future minimum lease payments under capital leases together with the present value of the net minimum lease payments as of March 31, 2014 are as follows:
		Yen in
		millions
	Year ending March 31:
	2015	¥	1,810
	2016		2,019
	2017		658
	2018		563
	2019		114
	2020 and thereafter		9
	Total minimum lease payments		5,173
	Less—Amount representing interest		(312	)
	Present value of net minimum lease payments		4,861
	Less—Current obligations		(1,667	)
	Long-term capital lease obligations	¥	3,194
Operating Leases of Lessee Disclosure	'
	The minimum rental payments required under operating leases relating primarily to land, buildings and equipment having initial or remaining non-cancelable lease terms in excess of one year as of March 31, 2014 are as follows:
		Yen in
		millions
	Year ending March 31:
	2015	¥	2,319
	2016		1,757
	2017		1,197
	2018		996
	2019		965
	2020 and thereafter		1,941
	Total minimum future rentals	¥	9,175
Schedule of Future Minimum Rental Payments for Operating Leases	'
	The future minimum lease payments to be received under operating leases that have remaining non-cancelable terms as of March 31, 2014 are as follows:
		Yen in
		millions
	Year ending March 31:
	2015	¥	31
	2016		25
	2017		25
	2018		26
	2019		26
	2020 and thereafter		91
	Total minimum future rentals	¥	224

Other_commitments_and_continge1

Other commitments and contingencies, concentrations and factors that may affect future operations (Tables)	12 Months Ended
	Mar. 31, 2014
Schedule of Product Warranty Liability	'
	The changes in product warranty liability for the years ended March 31, 2013 and 2014 are summarized as follows:
		Yen in millions
		March 31
		2013			2014
	Balance at beginning of year	¥	971		¥	2,201
	Addition		1,626			2,021
	Utilization		(664	)		(1,080	)
	Foreign exchange impact		268			(106	)
	Balance at end of year	¥	2,201		¥	3,036

Discontinued_Operations_Tables

Discontinued Operations (Tables)	12 Months Ended
	Mar. 31, 2014
Schedule of Disposal Groups, Including Discontinued Operations, Income Statement, Balance Sheet and Additional Disclosures	'
	Operating results of discontinued operations for the year ended March 31, 2012 were as follows:
		Yen in millions
		For the year ended
		March 31, 2012
		LAC			PGN			CLU			Total
		business			business			business
	Net sales	¥	1,576		¥	1,365		¥	2,674		¥	5,615
	Loss on discontinued operations before income taxes	¥	(2,203	)	¥	(1,817	)	¥	(3,776	)	¥	(7,796	)
	Income taxes		(269	)		129			168			28
	Loss on discontinued operations	¥	(2,472	)	¥	(1,688	)	¥	(3,608	)	¥	(7,768	)

Segment_information_Tables

Segment information (Tables)	12 Months Ended
	Mar. 31, 2014
Schedule of Entity-Wide Information, Revenue from External Customers by Products and Services	'
	The following table provides product information for the years ended March 31, 2012, 2013 and 2014:
			Yen in millions
			For the year ended
			March 31
			2012			2013			2014
	Net sales:
	Small precision motors:
	Hard disk drives spindle motors		¥	176,932		¥	165,427		¥	185,506
	Other small precision motors			154,505			154,297			177,007
	Sub-total			331,437			319,724			362,513
	Automotive, appliance, commercial and industrial products			208,529			248,464			345,236
	Machinery			64,904			63,526			86,955
	Electronic and optical components			69,377			69,188			72,845
	Others			8,073			8,368			7,560
	Consolidated total		¥	682,320		¥	709,270		¥	875,109
Schedule of Revenue from External Customers Attributed to Foreign Countries by Geographic Area	'
	Revenues from external customers, which are attributed to countries based on the location of the Company or the subsidiaries that transacted with the external customer for the years ended March 31, 2012, 2013 and 2014, and long-lived assets as of March 31, 2013 and 2014 are as follows:
			Yen in millions
			For the year ended
			March 31
			2012			2013			2014
	Net sales:
	Japan		¥	260,470		¥	213,169		¥	238,278
	U.S.A.			71,317			99,260			132,117
	Singapore			40,595			55,712			63,950
	Thailand			75,908			81,678			85,435
	The Philippines			19,683			18,543			24,506
	China			148,553			150,631			197,134
	Other			65,794			90,277			133,689
	Consolidated total		¥	682,320		¥	709,270		¥	875,109
			Yen in millions
			March 31
			2013			2014
	Long-lived assets:
	Japan		¥	86,612		¥	96,239
	U.S.A.			21,047			23,046
	Singapore			1,899			1,337
	Thailand			42,418			37,925
	The Philippines			11,838			12,904
	China			56,756			65,007
	Other			57,407			62,423
	Consolidated total		¥	277,977		¥	298,881
Schedule of Segment Reporting Information, by Segment	'
	The following tables show net sales to external customers and other financial information by operating segment for the years ended March 31, 2012, 2013 and 2014:
			Yen in millions
			For the year ended
			March 31
			2012			2013			2014
	Net sales to external customers:
	Nidec Corporation		¥	46,901		¥	23,748		¥	27,599
	Nidec Electronics (Thailand)			64,226			63,349			67,623
	Nidec (Zhejiang)			26,430			21,109			18,017
	Nidec (Dalian)			4,269			3,648			1,940
	Nidec Singapore			34,220			50,039			57,893
	Nidec (H.K.)			50,748			52,028			69,890
	Nidec Philippines			15,326			14,707			19,573
	Nidec Sankyo			78,589			73,201			98,564
	Nidec Copal			51,124			49,627			47,023
	Nidec Tosok			33,358			31,090			36,854
	Nidec Copal Electronics			29,098			26,845			31,295
	Nidec Techno Motor			40,058			39,940			50,691
	Nidec Motor			83,999			119,093			175,854
	Nidec Motors & Actuators			44,748			44,707			64,420
	All Others			78,268			96,236			106,996
	Total			681,362			709,367			874,232
	Adjustments *1			958			(97	)		877
	Consolidated total		¥	682,320		¥	709,270		¥	875,109
	*1	US GAAP adjustments primarily relate to the difference between recognition of revenue at the time of shipment and at the time of customer receipt.
			Yen in millions
			For the year ended
			March 31
			2012			2013			2014
	Net sales to other operating segments:
	Nidec Corporation		¥	100,064		¥	108,282		¥	138,354
	Nidec Electronics (Thailand)			36,649			35,492			43,982
	Nidec (Zhejiang)			3,617			2,977			5,011
	Nidec (Dalian)			15,471			11,117			10,559
	Nidec Singapore			448			709			749
	Nidec (H.K.)			1,162			1,734			1,339
	Nidec Philippines			24,390			25,682			29,266
	Nidec Sankyo			396			300			312
	Nidec Copal			2,318			2,093			2,318
	Nidec Tosok			150			190			171
	Nidec Copal Electronics			20			20			11
	Nidec Techno Motor			952			3,143			4,041
	Nidec Motor			30			154			80
	Nidec Motors & Actuators			11,607			15,170			20,213
	All Others			53,061			55,834			73,029
	Total			250,335			262,897			329,435
	Intersegment elimination			(250,335	)		(262,897	)		(329,435	)
	Consolidated total			—			—			—
			Yen in millions
			For the year ended
			March 31
			2012			2013			2014
	Operating income or loss:
	Nidec Corporation		¥	7,497		¥	(4,856	)	¥	4,865
	Nidec Electronics (Thailand)			15,027			10,525			12,781
	Nidec (Zhejiang)			774			(2,689	)		(243	)
	Nidec (Dalian)			431			(409	)		475
	Nidec Singapore			781			1,115			709
	Nidec (H.K.)			359			146			483
	Nidec Philippines			7,799			4,883			6,037
	Nidec Sankyo			7,414			4,181			10,392
	Nidec Copal			6,384			(3,192	)		(1,323	)
	Nidec Tosok			3,140			1,715			3,186
Nidec Copal Electronics			4,194			3,277			5,288
Nidec Techno Motor			4,591			4,168			6,671
Nidec Motor			2,111			723			9,314
Nidec Motors & Actuators			3,126			3,447			5,334
All Others			11,201			10,540			18,911
Total			74,829			33,574			82,880
Reclassification *1			(3,072	)		(17,606	)		2,055
U.S. GAAP adjustments and Others *2			(1,476	)		(537	)		(1,133	)
Consolidation adjustments mainly related to elimination of intersegment income or loss			2,789			2,167			1,266
		¥	73,070		¥	17,598		¥	85,068
*1	Some items are reclassified from other expenses (income) and included in operating expenses (income). Main reclassification is income or loss from sales or disposals of fixed assets for the year ended March 31, 2012, 2013 and 2014.
*2	Others is mainly from the amortization of identifiable intangible assets related to business combinations for the years ended March 31, 2012, 2013 and 2014.
		Yen in millions
		For the year ended
		March 31
		2012			2013			2014
Depreciation:
Nidec Corporation		¥	995		¥	917		¥	921
Nidec Electronics (Thailand)			5,085			5,572			5,502
Nidec (Zhejiang)			1,231			1,196			618
Nidec (Dalian)			802			914			359
Nidec Singapore			70			133			197
Nidec (H.K.)			6			7			6
Nidec Philippines			2,598			2,750			2,732
Nidec Sankyo			3,715			3,773			4,102
Nidec Copal			3,115			3,806			4,444
Nidec Tosok			2,660			2,930			3,775
Nidec Copal Electronics			1,150			1,318			1,283
Nidec Techno Motor			1,491			1,890			2,573
Nidec Motor			3,892			6,481			9,171
Nidec Motors & Actuators			1,423			1,470			2,186
All Others			4,297			5,265			6,537
Total			32,530			38,422			44,406
U.S. GAAP adjustments *1 and Others *2			(1,019	)		(3,487	)		(4,921	)
Consolidated total		¥	31,511		¥	34,935		¥	39,485
*1	Some leased assets are not capitalized in the operating segments but are capitalized under U.S. GAAP.
*2	The amount of each segment includes amortization of intangible assets. Others mainly represent adjustments to exclude the amortization of intangible assets in order to reconcile amounts to consolidated total of depreciation in consolidated statements of cash flows.
		Yen in millions
		March 31
		2013			2014
Segment assets:
Nidec Corporation		¥	565,451		¥	628,338
Nidec Electronics (Thailand)			91,784			116,476
Nidec (Zhejiang)			13,897			12,112
Nidec (Dalian)			24,159			20,763
Nidec Singapore			21,590			27,689
Nidec (H.K.)			15,678			22,458
Nidec Philippines			37,084			49,569
Nidec Sankyo			107,393			125,929
Nidec Copal			62,376			55,166
Nidec Tosok			43,566			50,221
Nidec Copal Electronics			38,684			42,115
Nidec Techno Motor			42,508			49,703
Nidec Motor			178,429			197,315
Nidec Motors & Actuators			46,601			68,405
All Others			158,388			217,075
Total			1,447,588			1,683,334
Elimination of intersegment assets, net of taxes			(579,766	)		(626,822	)
Identifiable intangible assets and other fair value adjustments			12,502			11,626
Goodwill			132,775			154,927
U.S.GAAP adjustments and Others *1			(7,682	)		(57,147	)
Consolidated total		¥	1,005,417		¥	1,165,918
*1	Others is mainly due to the reclassification of deferred tax assets and liabilities on consolidation.
		Yen in millions
		For the year ended
		March 31
		2013			2014
Capital expenditure for segment assets:
Nidec Corporation		¥	1,991		¥	1,884
Nidec Electronics (Thailand)			14,588			1,232
Nidec (Zhejiang)			710			712
Nidec (Dalian)			2,372			972
Nidec Singapore			417			9
Nidec (H.K.)			5			6
Nidec Philippines			1,876			3,368
Nidec Sankyo			4,777			3,712
Nidec Copal			9,539			2,427
Nidec Tosok			5,814			9,432
Nidec Copal Electronics			984			826
Nidec Techno Motor			5,144			3,549
Nidec Motor			3,594			4,134
Nidec Motors & Actuators			1,845			3,019
All Others			7,712			5,015
Consolidated total		¥	61,368		¥	40,297

Quarterly_Financial_Data_for_t1

Quarterly Financial Data for the year ended March 31, 2014 (Tables)	12 Months Ended
	Mar. 31, 2014
Schedule of Quarterly Financial Information	'
			Yen in millions
			First		Second		Third		Fourth		Total
			Quarter		Quarter		Quarter		Quarter
	Net sales		¥	211,276	¥	218,358	¥	217,091	¥	228,384	¥	875,109
	Income before income taxes			17,366		21,075		24,084		22,139		84,664
	Net income attributable to Nidec Corporation		¥	13,346	¥	13,757	¥	15,950	¥	13,351	¥	56,404
			Yen
	Net income attributable to Nidec Corporation per share:
	Basic *1			49.73		51.26		57.84		48.41		207.31
	Diluted *1			46.42		47.85		54.24		45.39		193.96
	Notes:
	*1:	Earnings-per-share amounts for each quarter are computed independently. As a result, their sum may not equal the total year earnings-per-share amounts.

Recovered_Sheet1

Summary of Significant Accounting Policies - Additional Information (Detail) (JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Significant Accounting Policies [Line Items]	'	'	'
Cash and cash equivalents, maximum original maturities of highly liquid investments	'three months or less	'	'
Depreciation	¥ 39,485	¥ 34,935	¥ 31,511
Advertising costs	¥ 477	¥ 296	¥ 228
Minimum percentage of likelihood of tax benefits being realized upon settlement in measurement of benefits from tax positions that meet the more-likely-than-not recognition threshold	50.00%	'	'
Proprietary technology	'	'	'
Significant Accounting Policies [Line Items]	'	'	'
Weighted average amortization period (in years)	'12 years	'	'
Customer relationships	'	'	'
Significant Accounting Policies [Line Items]	'	'	'
Weighted average amortization period (in years)	'18 years	'	'
Software	'	'	'
Significant Accounting Policies [Line Items]	'	'	'
Weighted average amortization period (in years)	'5 years	'	'
Other products factories | Minimum	'	'	'
Significant Accounting Policies [Line Items]	'	'	'
Property, plant and equipment, estimated useful life (in years)	'7 years	'	'
Other products factories | Maximum	'	'	'
Significant Accounting Policies [Line Items]	'	'	'
Property, plant and equipment, estimated useful life (in years)	'47 years	'	'
Head office and sales offices	'	'	'
Significant Accounting Policies [Line Items]	'	'	'
Property, plant and equipment, estimated useful life (in years)	'50 years	'	'
Leasehold Improvements | Minimum	'	'	'
Significant Accounting Policies [Line Items]	'	'	'
Property, plant and equipment, estimated useful life (in years)	'3 years	'	'
Leasehold Improvements | Maximum	'	'	'
Significant Accounting Policies [Line Items]	'	'	'
Property, plant and equipment, estimated useful life (in years)	'18 years	'	'
Machinery and Equipment | Minimum	'	'	'
Significant Accounting Policies [Line Items]	'	'	'
Property, plant and equipment, estimated useful life (in years)	'2 years	'	'
Machinery and Equipment | Maximum	'	'	'
Significant Accounting Policies [Line Items]	'	'	'
Property, plant and equipment, estimated useful life (in years)	'15 years	'	'

Acquisitions_Additional_Inform

Acquisitions - Additional Information (Detail) (JPY ¥)	0 Months Ended	12 Months Ended	1 Months Ended		0 Months Ended
In Millions, unless otherwise specified	Apr. 02, 2014	Mar. 31, 2014	Nov. 01, 2012	31-May-12	Apr. 02, 2012	Sep. 28, 2012	Oct. 02, 2012	Dec. 28, 2012	Jan. 02, 2014	Mar. 31, 2014
	Subsequent Event	Selling, General and Administrative Expenses	Kinetek Group Inc. ("Kinetek")	Ansaldo Sistemi Industriali S.p.A. ("Nidec ASI")	Minster Machine Company	Avtron Industrial Automation, Inc. ("Avtron")	SCD Co., Ltd.	Nidec Kaiyu Auto Electric (Jiangsu) Co., Ltd. ("Kaiyu")	Mitsubishi Materials C.M.I. Corporation ("CMI")	Honda Elesys Co., Ltd. ("Elesys")
Business Acquisition [Line Items]	'	'	'	'	'	'	'	'	'	'
Business acquisition, cash paid	'	'	¥ 35,697	¥ 36,564	¥ 9,202	¥ 4,861	¥ 3,305	¥ 1,018	¥ 5,228	¥ 24,320
Business acquisition, percentage of ownership acquired	'	'	'	'	'	'	51.40%	51.00%	'	'
Business acquisition, Acquisition-related cost	'	¥ 147	'	'	'	'	'	'	'	'
Common stock, stock split	2	'	'	'	'	'	'	'	'	'

Summary_of_Estimated_Fair_Valu

Summary of Estimated Fair Value of Assets Acquired and Liabilities Assumed at Acquisition Date (Detail) (JPY ¥)	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012	Jan. 02, 2014	Mar. 31, 2014
In Millions, unless otherwise specified				Mitsubishi Materials C.M.I. Corporation ("CMI")	Honda Elesys Co., Ltd. ("Elesys")
Business Acquisition [Line Items]	'	'	'	'	'
Cash and cash equivalents	'	'	'	¥ 1,081	¥ 5,759
Accounts receivable	'	'	'	1,323	5,176
Inventories	'	'	'	2,155	4,600
Other current assets	'	'	'	683	1,483
Property, plant and equipment	'	'	'	4,538	6,803
Goodwill	154,927	132,775	80,525	2,114	9,668
Intangible assets	'	'	'	55	58
Other non-current assets	'	'	'	790	657
Total assets acquired	'	'	'	12,739	34,204
Accounts payable	'	'	'	-1,420	-6,618
Other current liabilities	'	'	'	-2,834	-2,417
Other non-current liabilities	'	'	'	-3,256	-849
Total liabilities assumed	'	'	'	-7,510	-9,884
Noncontrolling interests	'	'	'	-1	'
Net assets acquired	'	'	'	¥ 5,228	¥ 24,320

Goodwill_Allocated_to_Operatin

Goodwill Allocated to Operating Segment (Detail) (JPY ¥)	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
In Millions, unless otherwise specified
Goodwill [Line Items]	'	'	'
Amount of Goodwill	¥ 154,927	¥ 132,775	¥ 80,525
Nidec Sankyo	'	'	'
Goodwill [Line Items]	'	'	'
Amount of Goodwill	29,533	27,312	26,100
All others	'	'	'
Goodwill [Line Items]	'	'	'
Amount of Goodwill	20,101	9,922	4,504
Mitsubishi Materials C.M.I. Corporation ("CMI") and Honda Elesys Co., Ltd. ("Elesys")	'	'	'
Goodwill [Line Items]	'	'	'
Amount of Goodwill	11,782	'	'
Amount of Goodwill deductible for tax purposes	727	'	'
Mitsubishi Materials C.M.I. Corporation ("CMI") and Honda Elesys Co., Ltd. ("Elesys") | Nidec Sankyo	'	'	'
Goodwill [Line Items]	'	'	'
Amount of Goodwill	2,114	'	'
Amount of Goodwill deductible for tax purposes	334	'	'
Mitsubishi Materials C.M.I. Corporation ("CMI") and Honda Elesys Co., Ltd. ("Elesys") | All others	'	'	'
Goodwill [Line Items]	'	'	'
Amount of Goodwill	9,668	'	'
Amount of Goodwill deductible for tax purposes	¥ 393	'	'

Pro_Forma_Results_of_Operation

Pro Forma Results of Operations (Detail) (JPY ¥)	12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Business Acquisition [Line Items]	'	'
Pro forma net sales	¥ 928,910	¥ 787,716
Pro forma net income	¥ 57,788	¥ 9,378
Pro forma net income attributable to Nidec Corporation per share	'	'
-basic	¥ 212.4	¥ 34.81
-diluted	¥ 198.72	¥ 32.32

Intangible_Assets_Subject_to_A

Intangible Assets Subject to Amortization (Detail) (JPY ¥)	Mar. 31, 2014	Mar. 31, 2013
In Millions, unless otherwise specified
Finite-Lived Intangible Assets [Line Items]	'	'
Gross carrying amounts	¥ 84,817	¥ 72,870
Accumulated amortization	24,131	16,089
Carrying amounts	60,686	56,781
Proprietary technology	'	'
Finite-Lived Intangible Assets [Line Items]	'	'
Gross carrying amounts	11,671	10,017
Accumulated amortization	2,535	1,469
Carrying amounts	9,136	8,548
Customer relationships	'	'
Finite-Lived Intangible Assets [Line Items]	'	'
Gross carrying amounts	48,157	43,305
Accumulated amortization	9,626	5,817
Carrying amounts	38,531	37,488
Software	'	'
Finite-Lived Intangible Assets [Line Items]	'	'
Gross carrying amounts	18,001	13,830
Accumulated amortization	8,625	6,878
Carrying amounts	9,376	6,952
Other	'	'
Finite-Lived Intangible Assets [Line Items]	'	'
Gross carrying amounts	6,988	5,718
Accumulated amortization	3,345	1,925
Carrying amounts	¥ 3,643	¥ 3,793

Recovered_Sheet2

Goodwill and Other Intangible Assets - Additional Information (Detail) (JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Goodwill and Intangible Assets Disclosure [Line Items]	'	'	'
Total amortization of intangible assets	¥ 6,377	¥ 4,627	¥ 2,664
Total indefinite lived intangible assets	¥ 7,920	¥ 7,208	'
Proprietary technology	'	'	'
Goodwill and Intangible Assets Disclosure [Line Items]	'	'	'
Weighted average amortization period (in years)	'12 years	'	'
Customer relationships	'	'	'
Goodwill and Intangible Assets Disclosure [Line Items]	'	'	'
Weighted average amortization period (in years)	'18 years	'	'
Software	'	'	'
Goodwill and Intangible Assets Disclosure [Line Items]	'	'	'
Weighted average amortization period (in years)	'5 years	'	'

Estimated_Aggregate_Amortizati

Estimated Aggregate Amortization Expense for Intangible Assets for Next Five Years (Detail) (JPY ¥)	Mar. 31, 2014
In Millions, unless otherwise specified
Expected Amortization Expense [Line Items]	'
2015	¥ 6,773
2016	6,445
2017	5,767
2018	5,123
2019	¥ 4,656

Changes_in_Carrying_Amount_of_

Changes in Carrying Amount of Goodwill (Detail) (JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Goodwill [Line Items]	'	'	'
Beginning Balance	¥ 132,775	¥ 80,525	'
Acquisition	11,782	40,962	'
Impairment loss	'	'	2,045
Translation adjustments and Others	10,370	11,288	'
Ending Balance	154,927	132,775	80,525
Nidec Electronics (Thailand)	'	'	'
Goodwill [Line Items]	'	'	'
Beginning Balance	6,994	6,109	'
Impairment loss	'	'	'
Translation adjustments and Others	651	885	'
Ending Balance	7,645	6,994	'
Nidec (Zhejiang)	'	'	'
Goodwill [Line Items]	'	'	'
Beginning Balance	1,044	912	'
Impairment loss	'	'	'
Translation adjustments and Others	98	132	'
Ending Balance	1,142	1,044	'
Nidec Sankyo	'	'	'
Goodwill [Line Items]	'	'	'
Beginning Balance	27,312	26,100	'
Acquisition	2,114	1,094	'
Impairment loss	'	'	'
Translation adjustments and Others	107	118	'
Ending Balance	29,533	27,312	'
Nidec Copal	'	'	'
Goodwill [Line Items]	'	'	'
Beginning Balance	16,462	16,462	'
Impairment loss	'	'	'
Ending Balance	16,462	16,462	'
Nidec Tosok	'	'	'
Goodwill [Line Items]	'	'	'
Beginning Balance	1,038	1,107	'
Impairment loss	'	'	'
Translation adjustments and Others	'	-69	'
Ending Balance	1,038	1,038	'
Nidec Copal Electronics	'	'	'
Goodwill [Line Items]	'	'	'
Beginning Balance	6,561	6,561	'
Impairment loss	'	'	'
Ending Balance	6,561	6,561	'
Nidec Techno Motor	'	'	'
Goodwill [Line Items]	'	'	'
Beginning Balance	2,049	2,049	'
Impairment loss	'	'	'
Ending Balance	2,049	2,049	'
Nidec Motor	'	'	'
Goodwill [Line Items]	'	'	'
Beginning Balance	55,008	11,984	'
Acquisition	'	34,021	'
Impairment loss	'	'	'
Translation adjustments and Others	8,070	9,003	'
Ending Balance	63,078	55,008	'
Nidec Motors & Actuators	'	'	'
Goodwill [Line Items]	'	'	'
Beginning Balance	6,385	4,737	'
Acquisition	'	1,062	'
Impairment loss	'	'	'
Translation adjustments and Others	933	586	'
Ending Balance	7,318	6,385	'
All others	'	'	'
Goodwill [Line Items]	'	'	'
Beginning Balance	9,922	4,504	'
Acquisition	9,668	4,785	'
Impairment loss	'	'	'
Translation adjustments and Others	511	633	'
Ending Balance	¥ 20,101	¥ 9,922	'

Supplemental_Information_Assoc

Supplemental Information Associated with the Consolidated Statements of Cash Flows (Detail) (JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Cash paid during the fiscal year for:	'	'	'
Income taxes	¥ 12,613	¥ 25,879	¥ 8,197
Interest	1,636	395	327
Non-cash investing and financing activities:	'	'	'
Capital leasing receivables	'	'	31
Capital lease obligations	499	206	214
Change in common stock in connection with share exchange transaction	4,279	3,270	'
Change in treasury stock in connection with share exchange transaction	¥ 20,655	¥ 16,710	'

Analysis_of_Activity_within_th

Analysis of Activity within the Allowance for Doubtful Accounts (Detail) (Allowance for Doubtful Accounts, JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Allowance for Doubtful Accounts	'	'	'
Accounts, Notes, Loans and Financing Receivable [Line Items]	'	'	'
Valuation allowance at beginning of year	¥ 1,375	¥ 1,002	¥ 1,013
Provision for doubtful accounts, net of reversal	366	166	30
Write-offs	-267	-90	-30
Translation adjustment and other	119	297	-11
Valuation allowance at end of year	¥ 1,593	¥ 1,375	¥ 1,002

Inventories_Detail

Inventories (Detail) (JPY ¥)	Mar. 31, 2014	Mar. 31, 2013
In Millions, unless otherwise specified
Inventory [Line Items]	'	'
Finished goods	¥ 51,293	¥ 42,599
Raw materials	39,993	30,839
Work in process	28,926	23,526
Supplies and other	3,669	2,862
Inventories	¥ 123,881	¥ 99,826

Other_Current_Assets_Detail

Other Current Assets (Detail) (JPY ¥)	Mar. 31, 2014	Mar. 31, 2013
In Millions, unless otherwise specified
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Line Items]	'	'
Other receivable	¥ 13,906	¥ 13,740
Deferred tax assets (Note 16)	10,434	12,787
Costs on uncompleted construction contracts	9,572	5,799
Prepaid expenses	5,225	4,079
Other	8,926	11,954
Other current assets	¥ 48,063	¥ 48,359

Recovered_Sheet3

Marketable Securities and Other Securities Investments, Debt and Equity Securities Aggregate Fair Value, Gross Unrealized Gains and Losses and Cost (Detail) (JPY ¥)	Mar. 31, 2014	Mar. 31, 2013
In Millions, unless otherwise specified
Investment Holdings [Line Items]	'	'
Cost	¥ 8,052	¥ 8,544
Gross unrealized gains	6,733	5,828
Gross unrealized losses	0	8
Fair value	14,785	14,364
Available-for-sale | Equity securities	'	'
Investment Holdings [Line Items]	'	'
Cost	7,652	7,838
Gross unrealized gains	6,731	5,814
Gross unrealized losses	0	3
Fair value	14,383	13,649
Available-for-sale | Debt Securities	'	'
Investment Holdings [Line Items]	'	'
Cost	'	405
Gross unrealized gains	'	11
Gross unrealized losses	'	5
Fair value	'	411
Held-to-maturity | Japanese government debt securities	'	'
Investment Holdings [Line Items]	'	'
Cost	400	301
Gross unrealized gains	2	3
Fair value	402	304
Fair Value, Estimate Not Practicable, Carrying (Reported) Amount | Equity securities	'	'
Investment Holdings [Line Items]	'	'
Cost	¥ 1,654	¥ 1,539

Recovered_Sheet4

Marketable Securities and Other Securities Investments - Additional Information (Detail) (JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Investment Holdings [Line Items]	'	'	'
Increase (decrease) in net unrealized gain on available-for-sale securities included as a component of accumulated other comprehensive income, net of applicable taxes	¥ 2,998	¥ 174	¥ (53)
Proceeds from sales of available-for-sale securities	1,059	692	100
Gross realized gains on sales of available-for-sale securities	242	347	0
Gross realized losses on sales of available-for-sale securities	12	0	0
Description of Impaired investment securities	'NIDEC presumes the value of investment securities is impaired if the fair value is below the original cost. Among the impaired investment securities, NIDEC presumes a decline in value of debt and equity securities is other-than-temporary if the fair value is significantly below the original cost for an extended period of time. The presumption of an other-than-temporary impairment may be overcome if there is evidence to support that the decline is temporary in nature due to the existence of other factors which overcome the duration or magnitude of the decline. On the other hand, even if a fair value is not significantly less than the original cost, the value of investment securities is impaired when specific factors indicate the decline in the fair value is other-than-temporary.	'	'
Held-to-maturity securities pledged as collateral for the deferred payments of certain taxes	¥ 400	¥ 301	'

Gross_Unrealized_Losses_on_and

Gross Unrealized Losses on, and Fair Value of Investment Securities, Aggregated by Investment Category and Length of Time that Individual investment Securities have been in a Continuous Unrealized Loss Position (Detail) (JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Gain (Loss) on Investments [Line Items]	'	'
Less than 12 months Fair value	¥ 0	¥ 198
Less than 12 months Unrealized loss	0	6
12 months or more Fair value	1	23
12 months or more Unrealized loss	0	2
Equity securities	'	'
Gain (Loss) on Investments [Line Items]	'	'
Less than 12 months Fair value	0	16
Less than 12 months Unrealized loss	0	1
12 months or more Fair value	1	23
12 months or more Unrealized loss	0	2
Debt Securities	'	'
Gain (Loss) on Investments [Line Items]	'	'
Less than 12 months Fair value	'	182
Less than 12 months Unrealized loss	'	¥ 5

Other_NonCurrent_Assets_Detail

Other Non-Current Assets (Detail) (JPY ¥)	Mar. 31, 2014		Mar. 31, 2013
In Millions, unless otherwise specified
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Line Items]	'		'
Intangible assets	¥ 68,606	[1]	¥ 63,989	[1]
Deferred tax assets	1,482		7,116
Other	7,599	[2]	5,810	[2]
Other non-current assets	¥ 77,687		¥ 76,915
[1]	"Intangible assets" information is described in Note 4 "Goodwill and other intangible assets"
[2]	"Other" primarily consists of Long-term prepaid expenses.

ShortTerm_Borrowings_Detail

Short-Term Borrowings (Detail) (JPY ¥)	Mar. 31, 2014	Mar. 31, 2013
In Millions, unless otherwise specified
Short-term Debt [Line Items]	'	'
Short-term borrowings	¥ 22,600	¥ 32,798
Notes Payable to Banks	'	'
Short-term Debt [Line Items]	'	'
Short-term borrowings	¥ 22,600	¥ 32,798

ShortTerm_Borrowings_Parenthet

Short-Term Borrowings (Parenthetical) (Detail) (Notes Payable to Banks)	Mar. 31, 2014	Mar. 31, 2013
Notes Payable to Banks	'	'
Short-term Debt [Line Items]	'	'
Short-term borrowings, average interest per annum	0.31%	0.21%

Recovered_Sheet5

Short-Term Borrowings and Long-Term Debt - Additional Information (Detail) (JPY ¥)	12 Months Ended	0 Months Ended		12 Months Ended		0 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 31, 2014	Apr. 02, 2014	Sep. 20, 2013	Mar. 31, 2014	Mar. 31, 2013	Apr. 02, 2014	Apr. 02, 2014
		Subsequent Event	Yen Denominated zero coupon convertible bonds due 2015	Yen Denominated zero coupon convertible bonds due 2015	Yen Denominated zero coupon convertible bonds due 2015	Yen Denominated zero coupon convertible bonds due 2015	Yen Denominated zero coupon convertible bonds due 2015
						Before stock split	After stock split
						Subsequent Event	Subsequent Event
Debt Disclosure [Line Items]	'	'	'	'	'	'	'
Unused lines of credit	¥ 228,674	'	'	'	'	'	'
Due date	'	'	'	18-Sep-15	'	'	'
Redemption price description	'	'	'	'redeemable at 100% of principal amount	'	'	'
Issue date	'	'	'	21-Sep-10	'	'	'
Redemption date	'	'	'	18-Sep-15	'	'	'
Conversion price	'	'	'	¥ 5,313	¥ 5,313	¥ 10,626	¥ 5,313
Number of convertible shares	'	'	'	18,021,833	'	9,010,916	18,021,833
Redemption price as percentage of principal amount	'	'	'	100.00%	'	'	'
Redemption of corporate bonds	¥ 4,250	'	¥ 4,250	'	'	'	'
Common stock, stock split	'	2	'	'	'	'	'

LongTerm_Debt_Detail

Long-Term Debt (Detail) (JPY ¥)	Mar. 31, 2014	Mar. 31, 2013
In Millions, unless otherwise specified
Debt Instrument [Line Items]	'	'
Long-term debt	¥ 77,804	¥ 73,925
Other long-term debt	245,991	200,347
Long-term debt and capital lease obligations	328,656	279,899
Less-Bonds current portion due within one year	-100	-100,247
Less-Long-term debt current portion due within one year	-27,478	-31,841
Less-Capital lease obligation current portion due within one year	-1,667	-1,540
Long-term portion	299,411	146,271
Long-term debt and capital lease obligations	328,656	279,899
Unsecured Debt	'	'
Debt Instrument [Line Items]	'	'
Long-term debt	77,804	73,925
Yen Denominated zero coupon convertible bonds due 2015	'	'
Debt Instrument [Line Items]	'	'
Long-term debt	95,891	100,247
Unsecured Zero Point Three Nine Percent Straight Bonds Due In Twenty Seventeen	'	'
Debt Instrument [Line Items]	'	'
Other long-term debt	65,000	65,000
Unsecured Zero Point Six Zero Percent Straight Bonds Due In Twenty Nineteen	'	'
Debt Instrument [Line Items]	'	'
Other long-term debt	15,000	15,000
Unsecured Zero Point Nine Six Percent Straight Bonds Due In Twenty Twenty Two	'	'
Debt Instrument [Line Items]	'	'
Other long-term debt	20,000	20,000
Unsecured Zero Point Two One Percent Straight Bonds Due In Twenty Sixteen	'	'
Debt Instrument [Line Items]	'	'
Other long-term debt	50,000	'
Unsecured Zero Point Seven Two Percent Straight Bonds Due In Twenty Fourteen	'	'
Debt Instrument [Line Items]	'	'
Other long-term debt	100	100
Capital Lease Obligations	'	'
Debt Instrument [Line Items]	'	'
Capital lease obligations	¥ 4,861	¥ 5,627

LongTerm_Debt_Parenthetical_De

Long-Term Debt (Parenthetical) (Detail) (JPY ¥)	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Yen Denominated zero coupon convertible bonds due 2015	'	'
Debt Instrument [Line Items]	'	'
Long-term debt, due date	'2015	'2015
Long-term debt, interest rate	0.00%	0.00%
Long-term debt, conversion price	¥ 5,313	¥ 5,313
Unsecured Zero Point Three Nine Percent Straight Bonds Due In Twenty Seventeen	'	'
Debt Instrument [Line Items]	'	'
Long-term debt, due date	'2017	'2017
Long-term debt, interest rate	0.39%	0.39%
Unsecured Zero Point Six Zero Percent Straight Bonds Due In Twenty Nineteen	'	'
Debt Instrument [Line Items]	'	'
Long-term debt, due date	'2019	'2019
Long-term debt, interest rate	0.60%	0.60%
Unsecured Zero Point Nine Six Percent Straight Bonds Due In Twenty Twenty Two	'	'
Debt Instrument [Line Items]	'	'
Long-term debt, due date	'2022	'2022
Long-term debt, interest rate	0.96%	0.96%
Unsecured Zero Point Two One Percent Straight Bonds Due In Twenty Sixteen	'	'
Debt Instrument [Line Items]	'	'
Long-term debt, due date	'2016	'2016
Long-term debt, interest rate	0.21%	0.21%
Unsecured Zero Point Seven Two Percent Straight Bonds Due In Twenty Fourteen	'	'
Debt Instrument [Line Items]	'	'
Long-term debt, due date	'2014	'2014
Long-term debt, interest rate	0.72%	0.72%
Minimum | Unsecured Debt	'	'
Debt Instrument [Line Items]	'	'
Long-term debt, due date	'2014	'2013
Long-term debt, interest rate	0.00%	0.00%
Minimum | Capital Lease Obligations	'	'
Debt Instrument [Line Items]	'	'
Long-term debt, due date	'2014	'2013
Long-term debt, interest rate	0.00%	0.00%
Maximum | Unsecured Debt	'	'
Debt Instrument [Line Items]	'	'
Long-term debt, due date	'2026	'2026
Long-term debt, interest rate	6.80%	6.40%
Maximum | Capital Lease Obligations	'	'
Debt Instrument [Line Items]	'	'
Long-term debt, due date	'2019	'2019
Long-term debt, interest rate	15.74%	8.27%

Detail_of_Zero_Coupon_Converti

Detail of Zero Coupon Convertible Bonds, Due 2015 (Detail) (JPY ¥)	Mar. 31, 2014	Mar. 31, 2013
In Millions, unless otherwise specified
Debt Instrument [Line Items]	'	'
Total	¥ 77,804	¥ 73,925
Yen Denominated zero coupon convertible bonds due 2015	'	'
Debt Instrument [Line Items]	'	'
Principal amount	95,750	100,000
Unamortized premium	141	247
Total	¥ 95,891	¥ 100,247

Aggregate_Amounts_of_Annual_Ma

Aggregate Amounts of Annual Maturity of Long-Term Debt During the Next Five Years (Detail) (JPY ¥)	Mar. 31, 2014
In Millions, unless otherwise specified
Debt Instrument [Line Items]	'
2015	¥ 29,245
2016	116,841
2017	81,153
2018	66,167
2019	137
2020 and thereafter	¥ 35,113

Other_Current_Liabilities_Deta

Other Current Liabilities (Detail) (JPY ¥)	Mar. 31, 2014	Mar. 31, 2013
In Millions, unless otherwise specified
Other Liabilities [Line Items]	'	'
Accounts payable for property, plant and equipment	¥ 9,857	¥ 10,354
Advances received	7,152	6,437
Income taxes payable	4,557	4,013
Other	11,576	11,628
Other current liabilities	¥ 33,142	¥ 32,432

Employees_Defined_Benefit_Plan

Employees' Defined Benefit Plans, Japanese plans (Detail) (JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Change in plan assets:	'	'
Fair value of plan assets at end of year	¥ 21,544	¥ 14,841
Japanese plans	'	'
Change in benefit obligation:	'	'
Benefit obligation at beginning of year	14,079	14,255
Service cost	927	910
Interest cost	180	197
Actuarial loss	196	163
Acquisition and other	4,014	26
Plan amendment	-143	'
Benefits paid	-1,851	-1,472
Defined Benefit Plan, Benefit Obligation	17,402	14,079
Change in plan assets:	'	'
Fair value of plan assets at beginning of year	7,827	7,096
Actual return on plan assets	576	823
Employer contribution	1,135	622
Acquisition and other	2,856	'
Benefits paid	-963	-714
Fair value of plan assets at end of year	11,431	7,827
Funded status	¥ (5,971)	¥ (6,252)

Amounts_Included_in_the_Consol

Amounts Included in the Consolidated Balance Sheet, Japanese Plans (Detail) (Japanese plans, JPY ¥)	Mar. 31, 2014	Mar. 31, 2013
In Millions, unless otherwise specified
Japanese plans	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Accrued pension and severance costs	¥ 6,045	¥ 6,272
Other non-current assets	-74	-20
Net amounts recognized	¥ 5,971	¥ 6,252

Amounts_Included_in_Accumulate

Amounts Included in Accumulated Other Comprehensive income (Loss) as Pension Liability Adjustments, Japanese Plans (Detail) (Japanese plans, JPY ¥)	Mar. 31, 2014	Mar. 31, 2013
In Millions, unless otherwise specified
Japanese plans	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Actuarial loss	¥ (1,562)	¥ (1,741)
Prior service credit	1,393	1,407
Pension liability adjustments, pre-tax	¥ (169)	¥ (334)

Pension_and_Severance_Plans_Ad

Pension and Severance Plans - Additional Information (Detail) (JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Defined Benefit Plan Disclosure [Line Items]	'	'	'
Defined benefit plans, expected employer contribute for the next fiscal year	¥ 1,477	'	'
Multiemployer plans, total amounts of cost recognized for contributions	156	'	'
Defined contribution plans, cost recognized for certain subsidiaries' contributions	2,617	1,999	1,533
Defined contribution plans, expected employer contribution	2,839	'	'
NTSC	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'
Multiemployer plans, total amounts of cost recognized for contributions	169	182	252
Equity securities	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'
Percentage of investments in securities or other investment vehicles	2.00%	'	'
Debt Securities	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'
Percentage of investments in securities or other investment vehicles	4.00%	'	'
Other than Securities Investment	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'
Percentage of investments in securities or other investment vehicles	94.00%	'	'
Japanese plans	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'
Accumulated benefit obligations	17,136	13,873	'
Estimated prior service cost (credit) for the defined benefit pension plans that will be amortized from accumulated other comprehensive income into benefits cost	157	'	'
Estimated net actuarial gain (loss) for the defined benefit pension plans that will be amortized from accumulated other comprehensive income into benefits cost	75	'	'
Foreign plans	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'
Accumulated benefit obligations	21,768	19,708	'
Estimated net actuarial gain (loss) for the defined benefit pension plans that will be amortized from accumulated other comprehensive income into benefits cost	¥ 12	'	'

Projected_Benefit_Obligation_A

Projected Benefit Obligation, Accumulated Benefit Obligation and Fair Value of Plan Assets, Japanese Plans (Detail) (Japanese plans, JPY ¥)	Mar. 31, 2014	Mar. 31, 2013
In Millions, unless otherwise specified
Japanese plans	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Projected benefit obligations	¥ 12,805	¥ 13,924
Accumulated benefit obligations	12,539	13,718
Fair value of plan assets	¥ 6,725	¥ 7,653

WeightedAverage_Assumptions_Us

Weighted-Average Assumptions Used to Determine Benefit Obligations, Japanese Plans (Detail) (Japanese plans)	Mar. 31, 2014	Mar. 31, 2013
Japanese plans	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Discount rate	1.20%	1.30%
Rate of compensation increase	4.20%	2.20%

Weighted_Average_Assumptions_U

Weighted Average Assumptions Used to Determine Net Pension and Severance Cost Japanese Plans (Detail) (Japanese plans)	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Japanese plans	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'
Discount rate	1.30%	1.60%	1.60%
Expected return on plan assets	2.60%	2.30%	2.30%
Rate of compensation increase	2.20%	2.30%	2.20%

Components_of_Net_Periodic_Ben

Components of Net Periodic (Benefit) Cost, Japanese Plans (Detail) (Japanese plans, JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Japanese plans	'	'	'
Components of net periodic (benefit) cost:	'	'	'
Service cost	¥ 927	¥ 910	¥ 983
Interest cost	180	197	213
Expected return on plan assets	-164	-139	-134
Amortization of net actuarial loss	92	123	120
Amortization of prior service credit	-157	-146	-171
Losses from curtailments and settlements	'	'	296
Net periodic pension cost	¥ 878	¥ 945	¥ 1,307

Employees_Defined_Benefit_Plan1

Employees' Defined Benefit Plans, Foreign Plans (Detail) (JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Change in plan assets:	'	'
Fair value of plan assets at end of year	¥ 21,544	¥ 14,841
Foreign plans	'	'
Change in benefit obligation:	'	'
Benefit obligation at beginning of year	19,966	6,119
Service cost	553	549
Interest cost	741	625
Actuarial loss (gain)	-548	992
Acquisition and other	131	10,171
Foreign currency exchange rate changes	2,155	2,297
Benefits paid	-1,032	-787
Defined Benefit Plan, Benefit Obligation	21,966	19,966
Change in plan assets:	'	'
Fair value of plan assets at beginning of year	7,014	563
Actual return on plan assets	957	505
Employer contribution	2,103	588
Acquisition and other	'	4,994
Foreign currency exchange rate changes	714	886
Benefits paid	-675	-522
Fair value of plan assets at end of year	10,113	7,014
Funded status	¥ (11,853)	¥ (12,952)

Amounts_Included_in_the_Consol1

Amounts Included in the Consolidated Balance Sheet, Foreign Plans (Detail) (Foreign plans, JPY ¥)	Mar. 31, 2014	Mar. 31, 2013
In Millions, unless otherwise specified
Foreign plans	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Accrued pension and severance costs	¥ 11,853	¥ 12,952
Net amounts recognized	¥ 11,853	¥ 12,952

Amounts_Included_in_Accumulate1

Amounts Included in Accumulated Other Comprehensive Income (Loss) as Pension Liability Adjustments, Foreign Plans (Detail) (Foreign plans, JPY ¥)	Mar. 31, 2014	Mar. 31, 2013
In Millions, unless otherwise specified
Foreign plans	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Actuarial loss	¥ 142	¥ (952)
Pension liability adjustments, pre-tax	¥ 142	¥ (952)

Projected_Benefit_Obligation_A1

Projected Benefit Obligation, Accumulated Benefit Obligation and Fair Value of Plan Assets, Foreign Plans (Detail) (Foreign plans, JPY ¥)	Mar. 31, 2014	Mar. 31, 2013
In Millions, unless otherwise specified
Foreign plans	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Projected benefit obligations	¥ 21,498	¥ 19,966
Accumulated benefit obligations	21,300	19,708
Fair value of plan assets	¥ 9,464	¥ 7,014

WeightedAverage_Assumptions_Us1

Weighted-Average Assumptions Used to Determine Benefit Obligations, Foreign Plans (Detail) (Foreign plans)	Mar. 31, 2014	Mar. 31, 2013
Foreign plans	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Discount rate	4.40%	4.40%
Rate of compensation increase	3.00%	3.00%

WeightedAverage_Assumptions_Us2

Weighted-Average Assumptions Used to Determine Net Pension and Severance Costs, Foreign Plans (Detail) (Foreign plans)	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Foreign plans	'	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'	'
Discount rate	4.40%	4.70%	5.70%
Expected return on plan assets	7.50%	7.50%	4.40%
Rate of compensation increase	3.00%	3.00%	2.90%

Components_of_Net_Periodic_Ben1

Components of Net Periodic (Benefit) Cost, Foreign Plans (Detail) (Foreign plans, JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Foreign plans	'	'	'
Components of net periodic (benefit) cost:	'	'	'
Service cost	¥ 553	¥ 549	¥ 441
Interest cost	741	625	230
Expected return on plan assets	-443	-445	-48
Amortization of net actuarial loss (gain)	27	6	-2
Net periodic pension cost	¥ 878	¥ 735	¥ 621

Fair_Value_of_Pension_Plan_Ass

Fair Value of Pension Plan Assets, by Asset Category (Detail) (JPY ¥)	Mar. 31, 2014		Mar. 31, 2013
In Millions, unless otherwise specified
Defined Benefit Plan Disclosure [Line Items]	'		'
Fair values of pension plan assets	¥ 21,544		¥ 14,841
Cash and cash equivalents	'		'
Defined Benefit Plan Disclosure [Line Items]	'		'
Fair values of pension plan assets	1,793		1,103
Life insurance company general	'		'
Defined Benefit Plan Disclosure [Line Items]	'		'
Fair values of pension plan assets	4,833		3,040
Pooled Funds	'		'
Defined Benefit Plan Disclosure [Line Items]	'		'
Fair values of pension plan assets	11,183	[1]	7,431	[2]
Others	'		'
Defined Benefit Plan Disclosure [Line Items]	'		'
Fair values of pension plan assets	2,464		2,070
Japanese companies Equity Securities	'		'
Defined Benefit Plan Disclosure [Line Items]	'		'
Fair values of pension plan assets	281		302
Foreign companies Equity Securities	'		'
Defined Benefit Plan Disclosure [Line Items]	'		'
Fair values of pension plan assets	233		302
Debt Securities | Pooled funds	'		'
Defined Benefit Plan Disclosure [Line Items]	'		'
Fair values of pension plan assets	757	[3]	593	[4]
Fair Value Measurements Using Inputs Considered as Level 1	'		'
Defined Benefit Plan Disclosure [Line Items]	'		'
Fair values of pension plan assets	2,307		1,707
Fair Value Measurements Using Inputs Considered as Level 1 | Cash and cash equivalents	'		'
Defined Benefit Plan Disclosure [Line Items]	'		'
Fair values of pension plan assets	1,793		1,103
Fair Value Measurements Using Inputs Considered as Level 1 | Japanese companies Equity Securities	'		'
Defined Benefit Plan Disclosure [Line Items]	'		'
Fair values of pension plan assets	281		302
Fair Value Measurements Using Inputs Considered as Level 1 | Foreign companies Equity Securities	'		'
Defined Benefit Plan Disclosure [Line Items]	'		'
Fair values of pension plan assets	233		302
Fair Value Measurements Using Inputs Considered as Level 2	'		'
Defined Benefit Plan Disclosure [Line Items]	'		'
Fair values of pension plan assets	19,237		11,064
Fair Value Measurements Using Inputs Considered as Level 2 | Life insurance company general	'		'
Defined Benefit Plan Disclosure [Line Items]	'		'
Fair values of pension plan assets	4,833		3,040
Fair Value Measurements Using Inputs Considered as Level 2 | Pooled Funds	'		'
Defined Benefit Plan Disclosure [Line Items]	'		'
Fair values of pension plan assets	11,183	[1]	7,431	[2]
Fair Value Measurements Using Inputs Considered as Level 2 | Others	'		'
Defined Benefit Plan Disclosure [Line Items]	'		'
Fair values of pension plan assets	2,464		'
Fair Value Measurements Using Inputs Considered as Level 2 | Debt Securities | Pooled funds	'		'
Defined Benefit Plan Disclosure [Line Items]	'		'
Fair values of pension plan assets	757	[3]	593	[4]
Fair Value Measurements Using Inputs Considered as Level 3	'		'
Defined Benefit Plan Disclosure [Line Items]	'		'
Fair values of pension plan assets	'		2,070
Fair Value Measurements Using Inputs Considered as Level 3 | Others	'		'
Defined Benefit Plan Disclosure [Line Items]	'		'
Fair values of pension plan assets	'		¥ 2,070
[1]	These funds primarily invest in listed equity securities consisting of approximately 7% Japanese companies and 31% foreign companies, and debt security consisting of approximately 6% Japanese bonds and 37% foreign bonds.
[2]	These funds primarily invest in listed equity securities consisting of approximately 12% Japanese companies and 60% foreign companies, and debt security consisting of approximately 9% Japanese bonds and 16% foreign bonds.
[3]	These funds invest in approximately 68% Japanese bonds, 32% foreign bonds.
[4]	These funds invest in approximately 86% Japanese bonds, 14% foreign bonds.

Fair_Value_of_Pension_Plan_Ass1

Fair Value of Pension Plan Assets, by Asset Category (Parenthetical) (Detail)	Mar. 31, 2014	Mar. 31, 2013
Japanese companies Equity Securities | Pooled Funds	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Percentage of investments in securities or other investment vehicles	7.00%	12.00%
Foreign companies Equity Securities | Pooled Funds	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Percentage of investments in securities or other investment vehicles	31.00%	60.00%
Japanese bonds | Pooled funds	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Percentage of investments in securities or other investment vehicles	68.00%	86.00%
Japanese bonds | Pooled Funds	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Percentage of investments in securities or other investment vehicles	6.00%	9.00%
Foreign bonds | Pooled funds	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Percentage of investments in securities or other investment vehicles	32.00%	14.00%
Foreign bonds | Pooled Funds	'	'
Defined Benefit Plan Disclosure [Line Items]	'	'
Percentage of investments in securities or other investment vehicles	37.00%	16.00%

Changes_in_Fair_Value_of_Plan_

Changes in Fair Value of Plan Assets Categorized as Level Three (Detail) (JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013
Defined Benefit Plan Disclosure [Line Items]	'		'
Fair value of plan assets at end of year	¥ 21,544		¥ 14,841
Fair Value Measurements Using Inputs Considered as Level 3	'		'
Defined Benefit Plan Disclosure [Line Items]	'		'
Fair value of plan assets at beginning of year	2,070		'
Purchases	'		582
Actual return on plan assets and other	394		329
Transfers out of level 3	-2,464	[1]	'
Fair value of plan assets at end of year	'		2,070
Fair Value Measurements Using Inputs Considered as Level 3 | Minster Machine Company	'		'
Defined Benefit Plan Disclosure [Line Items]	'		'
Acquisition	'		¥ 1,159	[2]
[1]	All the level 3 assets were transferred into level 2 because we got the ability to redeem the level 3 assets at net asset value at the measurement date.
[2]	As a result of the Acquisition of Minster, NIDEC acquired the plan assets categorized as Level 3.

Future_Benefit_Payments_for_De

Future Benefit Payments for Defined Benefit Plans (Detail) (JPY ¥)	Mar. 31, 2014
In Millions, unless otherwise specified
Japanese plans	'
Defined Benefit Plan Disclosure [Line Items]	'
2015	¥ 811
2016	932
2017	886
2018	892
2019	1,153
Years 2020-2024	5,667
Foreign plans	'
Defined Benefit Plan Disclosure [Line Items]	'
2015	1,030
2016	1,043
2017	942
2018	1,122
2019	1,121
Years 2020-2024	¥ 5,709

Other_LongTerm_Liabilities_Det

Other Long-Term Liabilities (Detail) (JPY ¥)	Mar. 31, 2014		Mar. 31, 2013
In Millions, unless otherwise specified
Other Liabilities [Line Items]	'		'
Deferred tax liabilities	¥ 17,138		¥ 14,715
Unrecognized tax benefits, accrued interest and penalty	2,321	[1]	2,173	[1]
Other	5,785		4,329
Other long-term liabilities	¥ 25,244		¥ 21,217
[1]	"Unrecognized tax benefits, accrued interest and penalty" information is described in Note 16 "Income taxes"

Equity_Additional_Information_

Equity - Additional Information (Detail) (JPY ¥)

12 Months Ended

1 Months Ended

1 Months Ended

1 Months Ended

12 Months Ended

In Millions, except Share data, unless otherwise specified

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Mar. 31, 2011

Mar. 31, 2014

Mar. 31, 2013

Oct. 31, 2012

Sep. 30, 2012

Oct. 31, 2013

Sep. 30, 2013

Oct. 31, 2013

Sep. 30, 2013

Mar. 31, 2014

Mar. 31, 2013

Shares Of Treasury Stock

Shares Of Treasury Stock

Nidec Sankyo

Nidec Sankyo

Nidec Copal

Nidec Copal

Nidec Tosok

Nidec Tosok

Repurchase at Board of Directors Meetings Resolution

Repurchase at Board of Directors Meetings Resolution

Stockholders Equity Note [Line Items]

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Percentage of cash dividends that must be appropriated as a legal reserve

'

'

'

10.00%

'

'

'

'

'

'

'

'

'

'

Description of dividend payment restriction

'

'

'

'No further appropriations are required when the sum of the legal reserves reaches 25% of stated capital. These reserves currently exceed 25% of stated capital and are available for dividends under the Company Law subject to approval at the shareholdersb meeting

'

'

'

'

'

'

'

'

'

'

Amount of statutory retained earnings of the Company available for dividend payments to shareholders

¥ 91,137

¥ 69,109

'

'

'

'

'

'

'

'

'

'

'

'

Retained earnings, cash dividends

7,585

'

'

'

'

'

'

'

'

'

'

'

'

'

Retained earnings, cash dividends per share

¥ 27.5

'

'

'

'

'

'

'

'

'

'

'

'

'

Purchase of treasury stock, shares

'

'

'

'

'

'

'

'

'

'

'

'

1,000,000

10,156,400

Purchase of treasury stock, value

2,838

31,277

10,155

'

'

'

'

'

'

'

'

'

2,696

31,209

Treasury stock, shares

14,343,952

20,787,044

'

'

14,343,952

20,311,044

'

'

'

'

'

'

'

'

Treasury stock, at cost, value

39,640

57,007

'

'

40,527

56,109

'

'

'

'

'

'

'

'

Purchase of additional interests in subsidiaries, shares of common stock held in treasury allocated for the share exchange

'

'

'

'

'

'

6,350,630

'

4,856,764

'

2,624,000

'

'

'

Purchase of additional interests in subsidiaries, percentage owned by parent company

'

'

'

'

'

'

100.00%

77.10%

100.00%

66.50%

100.00%

72.30%

'

'

Description of stock split

'The Company completed a two-for-one stock split.

'

'

'

'

'

'

'

'

'

'

'

'

'

Retained earnings relating to equity in undistributed earnings of accumulated deficit of equity method investee

¥ 168

¥ 152

¥ 190

'

'

'

'

'

'

'

'

'

'

'

Changes_in_Accumulated_Other_C

Changes in Accumulated Other Comprehensive Income (Loss) by Component (Detail) (JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]	'
Accumulated Other Comprehensive Income (Loss), Beginning balance	¥ 12,953
Other comprehensive income (loss) before reclassifications	45,558
Amounts reclassified from accumulated other comprehensive income (loss)	-135
Net change during the current period other comprehensive income (loss)	45,423
Accumulated Other Comprehensive Income (Loss), Ending balance	58,376
Foreign currency translation adjustments	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'
Accumulated Other Comprehensive Income (Loss), Beginning balance	12,636
Other comprehensive income (loss) before reclassifications	41,903
Net change during the current period other comprehensive income (loss)	41,903
Accumulated Other Comprehensive Income (Loss), Ending balance	54,539
Unrealized gains (losses) from securities	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'
Accumulated Other Comprehensive Income (Loss), Beginning balance	1,187
Other comprehensive income (loss) before reclassifications	3,145
Amounts reclassified from accumulated other comprehensive income (loss)	-147
Net change during the current period other comprehensive income (loss)	2,998
Accumulated Other Comprehensive Income (Loss), Ending balance	4,185
Unrealized gains (losses) from derivative instruments	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'
Accumulated Other Comprehensive Income (Loss), Beginning balance	242
Other comprehensive income (loss) before reclassifications	-244
Amounts reclassified from accumulated other comprehensive income (loss)	-22
Net change during the current period other comprehensive income (loss)	-266
Accumulated Other Comprehensive Income (Loss), Ending balance	-24
Pension liability adjustments	'
Accumulated Other Comprehensive Income (Loss) [Line Items]	'
Accumulated Other Comprehensive Income (Loss), Beginning balance	-1,112
Other comprehensive income (loss) before reclassifications	754
Amounts reclassified from accumulated other comprehensive income (loss)	34
Net change during the current period other comprehensive income (loss)	788
Accumulated Other Comprehensive Income (Loss), Ending balance	¥ (324)

Reclassification_Out_of_Accumu

Reclassification Out of Accumulated Other Comprehensive Income (Loss) (Detail) (JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013	Mar. 31, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]	'		'	'
(Loss) gain on marketable securities, net	¥ 245		¥ (87)	¥ (202)
Cost of products sold, Interest expense.	674,699		572,634	523,729
Income taxes	25,729		6,562	18,801
Consolidated net income	58,910		6,849	44,287
Net (income) loss attributable to noncontrolling interests	2,506		-1,137	3,556
Net income attributable to Nidec Corporation	56,404		7,986	40,731
Reclassification out of Accumulated Other Comprehensive Income	'		'	'
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]	'		'	'
Net income attributable to Nidec Corporation	-135	[1]	'	'
Reclassification out of Accumulated Other Comprehensive Income | Unrealized gains (losses) from securities	'		'	'
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]	'		'	'
(Loss) gain on marketable securities, net	-230	[1]	'	'
Income taxes	83	[1]	'	'
Consolidated net income	-147	[1]	'	'
Net income attributable to Nidec Corporation	-147	[1]	'	'
Reclassification out of Accumulated Other Comprehensive Income | Unrealized gains (losses) from derivative instruments	'		'	'
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]	'		'	'
Cost of products sold, Interest expense.	-37	[1]	'	'
Income taxes	15	[1]	'	'
Consolidated net income	-22	[1]	'	'
Net income attributable to Nidec Corporation	-22	[1]	'	'
Reclassification out of Accumulated Other Comprehensive Income | Pension liability adjustments	'		'	'
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]	'		'	'
Net periodic pension cost	-38	[1],[2]	'	'
Income taxes	22	[1]	'	'
Consolidated net income	-16	[1]	'	'
Net (income) loss attributable to noncontrolling interests	50	[1]	'	'
Net income attributable to Nidec Corporation	¥ 34	[1]	'	'
[1]	Amounts in parentheses indicate gains in consolidated statement of income.
[2]	This accumulated other comprehensive income (loss) component is included in the computation of net periodic pension cost.

Tax_Effects_Allocated_to_Each_

Tax Effects Allocated to Each Component of Other Comprehensive Income (Loss) and Reclassification Adjustments, Including Amounts Attributable to Noncontrolling Interests (Detail) (JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Foreign currency translation adjustments, Pre-tax	'	'	'
Foreign currency translation adjustments arising during period, Pre-tax	¥ 43,429	¥ 62,024	¥ (2,665)
Reclassification adjustments for gains and losses realized in net income, Pre-tax	'	134	105
Unrealized gains (losses) from securities, Pre-tax	'	'	'
Unrealized holding gains (losses) arising during period, Pre-tax	4,567	156	-358
Reclassification adjustments for gains and losses realized in net income, Pre-tax	-230	88	253
Unrealized gains (losses) from derivative instruments qualifying for cash flow hedges, Pre-tax	'	'	'
Unrealized gains (losses) arising during period, Pre-tax	-397	93	-541
Reclassification adjustments for gains and losses realized in net income, Pre-tax	-37	196	291
Pension liability adjustment, Pre-tax	'	'	'
Actuarial gains arising during period, Pre-tax	1,071	-328	-831
Prior service credit (cost) arising during period, Pre-tax	74	'	-10
Reclassification adjustments for actuarial gains and losses realized in net income, Pre-tax	119	130	891
Reclassification adjustments for prior service credit and cost realized in net income, Pre-tax	-157	-152	463
Other comprehensive income (loss), Pre-tax	48,439	62,341	-2,402
Foreign currency translation adjustments, Tax benefit (expense)	'	'	'
Foreign currency translation adjustments arising during period, Tax benefit (expense)	'	'	'
Reclassification adjustments for gains and losses realized in net income, Tax benefit (expense)	'	'	'
Unrealized gains (losses) from securities, Tax benefit (expense)	'	'	'
Unrealized holding gains (losses) arising during period, Tax benefit (expense)	-1,440	-56	129
Reclassification adjustments for gains and losses realized in net income, Tax benefit (expense)	83	-37	-31
Unrealized gains (losses) from derivative instruments qualifying for cash flow hedges, Tax benefit (expense)	'	'	'
Unrealized gains (losses) arising during period, Tax benefit (expense)	153	-30	216
Reclassification adjustments for gains and losses realized in net income, Tax benefit (expense)	15	-90	-112
Pension liability adjustment, Tax benefit (expense)	'	'	'
Actuarial gains arising during period, Tax benefit (expense)	-378	-93	114
Prior service credit (cost) arising during period, Tax benefit (expense)	-14	'	4
Reclassification adjustments for actuarial gains and losses realized in net income, Tax benefit (expense)	-35	-45	-340
Reclassification adjustments for prior service credit and cost realized in net income, Tax benefit (expense)	57	55	-198
Other comprehensive income (loss), Tax benefit (expense)	-1,559	-296	-218
Foreign currency translation adjustments, Net-of-tax	'	'	'
Foreign currency translation adjustments arising during period, Net-of-tax	43,429	62,024	-2,665
Reclassification adjustments for gains and losses realized in net income, Net-of-tax	'	134	105
Unrealized gains (losses) from securities, Net-of-tax	'	'	'
Unrealized holding gains (losses) arising during period, Net-of-tax	3,127	100	-229
Reclassification adjustments for gains and losses realized in net income, Net-of-tax	-147	51	222
Unrealized gains (losses) from derivative instruments qualifying for cash flow hedges, Net-of-tax	'	'	'
Unrealized gains (losses) arising during period, Net-of-tax	-244	63	-325
Reclassification adjustments for gains and losses realized in net income, Net-of-tax	-22	106	179
Pension liability adjustment, Net-of-tax	'	'	'
Actuarial gains arising during period, Net-of-tax	693	-421	-717
Prior service credit (cost) arising during period, Net-of-tax	60	'	-6
Reclassification adjustments for actuarial gains and losses realized in net income, Net-of-tax	84	85	551
Reclassification adjustments for prior service credit and cost realized in net income, Net-of-tax	-100	-97	265
Other comprehensive income (loss), Net-of-tax	¥ 46,880	¥ 62,045	¥ (2,620)

Components_of_Income_from_Cont

Components of Income from Continuing Operations Before Income Tax (Detail) (JPY ¥)	3 Months Ended				12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Schedule of Components of Income Before Income Tax Expense (Benefit) [Line Items]	'	'	'	'	'	'	'
Income from continuing operations before income taxes	¥ 22,139	¥ 24,084	¥ 21,075	¥ 17,366	¥ 84,664	¥ 13,398	¥ 70,856
The Company and domestic subsidiaries	'	'	'	'	'	'	'
Schedule of Components of Income Before Income Tax Expense (Benefit) [Line Items]	'	'	'	'	'	'	'
Income from continuing operations before income taxes	'	'	'	'	25,463	-7,473	46,181
Foreign Subsidiaries	'	'	'	'	'	'	'
Schedule of Components of Income Before Income Tax Expense (Benefit) [Line Items]	'	'	'	'	'	'	'
Income from continuing operations before income taxes	'	'	'	'	¥ 59,201	¥ 20,871	¥ 24,675

Provision_for_Income_Taxes_Det

Provision for Income Taxes (Detail) (JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Current income tax expense/(benefit):	'	'	'
The Company and domestic subsidiaries	¥ 1,872	¥ 9,200	¥ (4,462)
Foreign subsidiaries	10,139	5,713	6,694
Total current	12,011	14,913	2,232
Deferred income tax expense (benefit):	'	'	'
The Company and domestic subsidiaries	12,649	-5,504	16,289
Foreign subsidiaries	1,069	-2,847	280
Total deferred	13,718	-8,351	16,569
Total provision	¥ 25,729	¥ 6,562	¥ 18,801

Income_Taxes_Additional_Inform

Income Taxes - Additional Information (Detail) (JPY ¥)	12 Months Ended				12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2014	Mar. 31, 2014	Mar. 31, 2014	Sep. 30, 2011
				Operating loss carryforwards with no expiration date	Foreign Subsidiaries	Thailand	The Philippines
Income Taxes [Line Items]	'	'	'	'	'	'	'
Statutory income tax rate	38.00%	38.00%	41.00%	'	'	'	'
Effective income tax rate, decrease from previous year	-18.60%	'	'	'	-29.00%	'	'
Effective income tax rate	30.40%	49.00%	26.50%	'	'	'	'
Tax benefit in foreign subsidiaries	-14.60%	-43.60%	-16.10%	'	'	'	'
Income tax incentives and privileges, exemption period	'	'	'	'	'	'For a period of eight years	'Four years
Operating loss carryforwards	¥ 35,843	'	'	¥ 6,245	'	'	'
Operating loss carryforwards, expiration period	'Expire at various dates primarily up to 9 years	'	'	'	'	'	'
Undistributed earnings of foreign subsidiaries	157,931	'	'	'	'	'	'
Undistributed earnings of foreign subsidiaries, future estimated additional deferred tax liability	11,558	'	'	'	'	'	'
Unrecognized tax benefits that, if recognized, would reduce the effective tax rate	2,232	'	'	'	'	'	'
Unrecognized tax benefit, total gross accrued interest and penalty	¥ 89	¥ 192	'	'	'	'	'

Reconciliation_of_Differences_

Reconciliation of Differences Between the Statutory Tax Rate and the Effective Income Tax Rate (Detail)	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Reconciliation of Statutory Federal Tax Rate [Line Items]	'	'	'
Statutory tax rate	38.00%	38.00%	41.00%
Increase (reduction) in taxes resulting from:	'	'	'
Tax benefit in foreign subsidiaries	-14.60%	-43.60%	-16.10%
Tax on undistributed earnings	2.20%	8.90%	5.10%
Valuation allowance	-2.30%	33.70%	4.10%
Liabilities for unrecognized tax benefits	-0.10%	2.30%	-10.50%
Reversal of deferred tax assets related to foreign tax credit	5.30%	'	'
Changes in Japanese income tax rates	0.30%	'	1.40%
Other	1.60%	9.70%	1.50%
Effective income tax rate	30.40%	49.00%	26.50%

Aggregate_Dollar_and_Per_Share

Aggregate Dollar and Per Share Effects of Tax Holidays (Detail) (JPY ¥)	12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Income Tax Holiday [Line Items]	'	'	'
Aggregate amounts of tax holidays	¥ 4,362	¥ 2,968	¥ 4,023
Basic Earnings Per Share	'	'	'
Income Tax Holiday [Line Items]	'	'	'
Per Share Effects of tax holidays	¥ 16.03	¥ 11.02	¥ 14.63
Diluted Earnings Per Share	'	'	'
Income Tax Holiday [Line Items]	'	'	'
Per Share Effects of tax holidays	¥ 15.02	¥ 10.3	¥ 13.69

Significant_Components_of_Defe

Significant Components of Deferred Tax Assets and Liabilities (Detail) (JPY ¥)	Mar. 31, 2014	Mar. 31, 2013
In Millions, unless otherwise specified
Deferred tax assets:	'	'
Inventories	¥ 2,818	¥ 3,142
Marketable securities	'	1,102
Property, plant and equipment	5,019	'
Accrued bonus	2,330	2,242
Accrued enterprise tax	221	'
Pension and severance plans	4,464	4,526
Operating loss carryforwards for tax purposes	12,811	13,646
Foreign tax credit	'	5,402
Accrued vacation	1,090	1,135
Accrued expenses	1,421	3,636
Other	2,666	2,613
Gross deferred tax assets	32,840	37,444
Less-Valuation allowance	-14,561	-14,492
Net deferred tax assets	18,279	22,952
Deferred tax liabilities:	'	'
Refund of enterprise taxes	'	-285
Basis difference of acquired assets	-458	-4,495
Property, plant and equipment	'	-1,058
Undistributed earnings not permanently reinvested	-9,311	-7,856
Marketable securities	-321	'
Intangible assets	-9,813	-4,816
Other	-5,181	-1,083
Gross deferred tax liabilities	-25,084	-19,593
Net deferred tax assets	¥ (6,805)	¥ 3,359

Net_Changes_in_the_Total_Valua

Net Changes in the Total Valuation Allowance for Deferred Tax Assets (Detail) (Valuation Allowance of Deferred Tax Assets, JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Valuation Allowance of Deferred Tax Assets	'	'	'
Valuation Allowance [Line Items]	'	'	'
Valuation allowance at beginning of year	¥ (14,492)	¥ (9,786)	¥ (6,235)
Additions	-4,231	-7,660	-3,490
Deductions	4,183	2,994	1,581
Impact on newly acquired companies	-21	-40	-1,642
Valuation allowance at end of year	¥ (14,561)	¥ (14,492)	¥ (9,786)

Net_Deferred_Tax_Assets_Includ

Net Deferred Tax Assets Included in the Consolidated Balance Sheets (Detail) (JPY ¥)	Mar. 31, 2014	Mar. 31, 2013
In Millions, unless otherwise specified
Deferred tax assets:	'	'
Other current assets	¥ 10,434	¥ 12,787
Other non-current assets	1,482	7,116
Deferred tax liabilities:	'	'
Other current liabilities	-1,583	-1,829
Other long-term liabilities	-17,138	-14,715
Net deferred tax assets	¥ (6,805)	¥ 3,359

Reconciliation_of_the_Beginnin

Reconciliation of the Beginning and Ending Amount of Unrecognized Tax Benefits (Detail) (JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Income Tax Contingency [Line Items]	'	'	'
Balance at beginning of year	¥ 2,361	¥ 1,766	¥ 9,199
Additions for tax positions of the current year	357	44	1,766
Additions for tax positions of prior years	'	551	'
Reduction for tax positions of prior years	-486	'	'
Settlements	'	'	-9,199
Balance at end of year	¥ 2,232	¥ 2,361	¥ 1,766

Reconciliation_of_Differences_1

Reconciliation of Differences Between Basic and Diluted Income Attributable to Nidec Corporation Per Share (Detail) (JPY ¥)

3 Months Ended

12 Months Ended

In Millions, except Share data in Thousands, unless otherwise specified

Mar. 31, 2014

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2014

Mar. 31, 2013

Mar. 31, 2012

Basic net income attributable to Nidec Corporation per share:

'

'

'

'

'

'

'

Income from continuing operations attributable to Nidec Corporation

'

'

'

'

¥ 56,404

¥ 7,986

¥ 46,242

Loss on discontinued operations attributable to Nidec Corporation

'

'

'

'

'

'

-5,511

Net income attributable to Nidec Corporation

13,351

15,950

13,757

13,346

56,404

7,986

40,731

Diluted net income attributable to Nidec Corporation per share:

'

'

'

'

'

'

'

Income from continuing operations attributable to Nidec Corporation

'

'

'

'

56,340

7,925

40,676

Weighted-average shares, basic:

'

'

'

'

'

'

'

Weighted-average shares, basic

'

'

'

'

272,078

269,429

274,981

Effect of dilutive securities

'

'

'

'

'

'

'

Zero coupon convertible bonds

'

'

'

'

18,400

18,821

18,821

Weighted-average shares, diluted:

'

'

'

'

'

'

'

Weighted-average shares, diluted

'

'

'

'

290,478

288,250

293,802

Basic net income attributable to Nidec Corporation per share

'

'

'

'

'

'

'

Income from continuing operations attributable to Nidec Corporation

'

'

'

'

¥ 207.31

¥ 29.64

¥ 168.16

Loss on discontinued operations attributable to Nidec Corporation

'

'

'

'

'

'

¥ (20.04)

Net income attributable to Nidec Corporation

¥ 48.41

[1]

¥ 57.84

[1]

¥ 51.26

[1]

¥ 49.73

[1]

¥ 207.31

[1]

¥ 29.64

¥ 148.12

Diluted net income attributable to Nidec Corporation per share

'

'

'

'

'

'

'

Income from continuing operations attributable to Nidec Corporation

'

'

'

'

¥ 193.96

¥ 27.49

¥ 157.2

Loss on discontinued operations attributable to Nidec Corporation

'

'

'

'

'

'

¥ (18.75)

Net income attributable to Nidec Corporation

¥ 45.39

[1]

¥ 54.24

[1]

¥ 47.85

[1]

¥ 46.42

[1]

¥ 193.96

[1]

¥ 27.49

¥ 138.45

Segment, Continuing Operations

'

'

'

'

'

'

'

Diluted net income attributable to Nidec Corporation per share:

'

'

'

'

'

'

'

Income from continuing operations attributable to Nidec Corporation

'

'

'

'

'

'

46,187

Weighted-average shares, basic:

'

'

'

'

'

'

'

Weighted-average shares, basic

'

'

'

'

'

'

274,981

Weighted-average shares, diluted:

'

'

'

'

'

'

'

Weighted-average shares, diluted

'

'

'

'

'

'

293,802

Segment, Discontinued Operations

'

'

'

'

'

'

'

Diluted net income attributable to Nidec Corporation per share:

'

'

'

'

'

'

'

Income from continuing operations attributable to Nidec Corporation

'

'

'

'

'

'

-5,511

Weighted-average shares, basic:

'

'

'

'

'

'

'

Weighted-average shares, basic

'

'

'

'

'

'

274,981

Weighted-average shares, diluted:

'

'

'

'

'

'

'

Weighted-average shares, diluted

'

'

'

'

'

'

293,802

Yen Denominated zero coupon convertible bonds due 2015

'

'

'

'

'

'

'

Effect of dilutive securities:

'

'

'

'

'

'

'

Zero coupon convertible bonds

'

'

'

'

¥ (64)

¥ (61)

¥ (55)

[1]

Earnings-per-share amounts for each quarter are computed independently. As a result, their sum may not equal the total year earnings-per-share amounts.

Recovered_Sheet6

Reconciliation of the Differences Between Basic and Diluted Earnings Per Share - Additional Information (Detail) (Subsequent Event)	0 Months Ended
	Apr. 02, 2014
Subsequent Event	'
Earnings Per Share Note [Line Items]	'
Common stock, stock split	2

Contracted_Amounts_Outstanding

Contracted Amounts Outstanding of Derivative Instruments (Detail) (JPY ¥)	Mar. 31, 2014	Mar. 31, 2013
In Millions, unless otherwise specified
Designated as Hedging Instrument | Foreign exchange forward contracts	'	'
Derivative [Line Items]	'	'
Contractual amounts	¥ 9,736	¥ 7,403
Designated as Hedging Instrument | Interest rate swap agreement	'	'
Derivative [Line Items]	'	'
Contractual amounts	20,587	32,205
Designated as Hedging Instrument | Commodity futures	'	'
Derivative [Line Items]	'	'
Contractual amounts	4,610	3,739
Not Designated as Hedging Instrument | Foreign exchange forward contracts	'	'
Derivative [Line Items]	'	'
Contractual amounts	1,800	149
Not Designated as Hedging Instrument | Currency option contracts	'	'
Derivative [Line Items]	'	'
Contractual amounts	¥ 53	¥ 231

Fair_Value_of_Derivative_Instr

Fair Value of Derivative Instruments (Detail) (JPY ¥)	Mar. 31, 2014	Mar. 31, 2013
In Millions, unless otherwise specified
Designated as Hedging Instrument | Foreign exchange forward contracts | Other current assets	'	'
Derivative [Line Items]	'	'
Asset Derivatives	¥ 271	¥ 659
Designated as Hedging Instrument | Foreign exchange forward contracts | Other current liabilities	'	'
Derivative [Line Items]	'	'
Liability Derivatives	1	22
Designated as Hedging Instrument | Commodity futures | Other current liabilities	'	'
Derivative [Line Items]	'	'
Liability Derivatives	239	181
Designated as Hedging Instrument | Interest rate swap agreement | Other current liabilities	'	'
Derivative [Line Items]	'	'
Liability Derivatives	31	20
Not Designated as Hedging Instrument | Foreign exchange forward contracts | Other current assets	'	'
Derivative [Line Items]	'	'
Asset Derivatives	4	16
Not Designated as Hedging Instrument | Currency option contracts | Other current assets	'	'
Derivative [Line Items]	'	'
Asset Derivatives	¥ 7	¥ 10

Effect_of_Derivative_Instrumen

Effect of Derivative Instruments on the Consolidated Statements of Income (Detail) (JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Designated as Hedging Instrument | Foreign exchange forward contracts	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'
Gains (losses) recognized in accumulated other comprehensive income	¥ (229)	¥ 277	¥ (68)
Designated as Hedging Instrument | Foreign exchange forward contracts | Cost of Sales	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'
Gains (losses) reclassified from accumulated other comprehensive income into income (effective portion)	241	81	17
Designated as Hedging Instrument | Interest Rate Swap	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'
Gains (losses) recognized in accumulated other comprehensive income	-5	-6	'
Designated as Hedging Instrument | Commodity futures	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'
Gains (losses) recognized in accumulated other comprehensive income	-32	-102	-78
Designated as Hedging Instrument | Commodity futures | Cost of Sales	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'
Gains (losses) reclassified from accumulated other comprehensive income into income (effective portion)	-212	-183	-196
Designated as Hedging Instrument | Interest rate swap agreement | Interest Expense	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'
Gains (losses) reclassified from accumulated other comprehensive income into income (effective portion)	-7	-4	'
Not Designated as Hedging Instrument | Foreign exchange forward contracts | Foreign Exchange	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'
Gains (losses) recognized in income	23	22	'
Not Designated as Hedging Instrument | Currency option contracts | Foreign Exchange	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'
Gains (losses) recognized in income	18	40	'
Not Designated as Hedging Instrument | Interest rate swap agreement | Other Income	'	'	'
Derivative Instruments, Gain (Loss) [Line Items]	'	'	'
Gains (losses) recognized in income	'	'	¥ 2

Derivatives_Additional_Informa

Derivatives - Additional Information (Detail) (JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014
Derivative [Line Items]	'
Net loss in accumulated other comprehensive income expected to be reclassified into earnings within the next 12 months	¥ (27)
The maximum length of time over which NIDEC hedged its exposure to variability in future cash flows for forecasted transactions	'23 years

Assets_and_Liabilities_that_ar

Assets and Liabilities that are Measured at Fair Value on a Recurring Basis (Detail) (Fair Value, Measurements, Recurring, JPY ¥)	Mar. 31, 2014	Mar. 31, 2013
In Millions, unless otherwise specified
Assets:	'	'
Marketable securities	¥ 14,383	¥ 14,060
Derivatives	282	685
Total assets:	14,665	14,745
Liabilities:	'	'
Derivatives	271	223
Fair Value Measurements Using Inputs Considered as Level 1	'	'
Assets:	'	'
Marketable securities	14,383	13,649
Total assets:	14,383	13,649
Liabilities:	'	'
Derivatives	239	181
Fair Value Measurements Using Inputs Considered as Level 2	'	'
Assets:	'	'
Marketable securities	'	411
Derivatives	282	685
Total assets:	282	1,096
Liabilities:	'	'
Derivatives	¥ 32	¥ 42

Carrying_Amount_and_Estimated_

Carrying Amount and Estimated Fair Values of Financial Instruments (Detail) (JPY ¥)	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
In Millions, unless otherwise specified
Carrying amount of Asset (Liability)	'	'	'	'
Cash and cash equivalents	¥ 247,740	¥ 193,420	¥ 130,290	¥ 94,321
Short-term investments	2,344	1,552	'	'
Long-term investments	83	'	'	'
Short-term loan receivable	157	132	'	'
Long-term loan receivable	48	89	'	'
Short-term borrowings	-22,600	-32,798	'	'
Long-term debt including the current portion and excluding capital lease obligation and bonds	-77,804	-73,925	'	'
Bonds including the current portion	-245,991	-200,347	'	'
Estimated fair value Asset (Liability)	'	'	'	'
Cash and cash equivalents	247,740	193,420	'	'
Short-term investments	2,344	1,552	'	'
Long-term investments	82	'	'	'
Short-term borrowings	-22,600	-32,798	'	'
Long-term debt including the current portion and excluding capital lease obligation and bonds	-77,486	-73,907	'	'
Bonds including the current portion	-271,853	-200,850	'	'
Short-term loan receivable	'	'	'	'
Estimated fair value Asset (Liability)	'	'	'	'
Loan receivable	157	132	'	'
Long-term loan receivable	'	'	'	'
Estimated fair value Asset (Liability)	'	'	'	'
Loan receivable	¥ 50	¥ 91	'	'

Related_Party_Transactions_Add

Related Party Transactions - Additional Information (Detail)	1 Months Ended
	Oct. 31, 2013	Oct. 31, 2012	Mar. 31, 2014
Nidec Sankyo	'	'	'
Related Party Transaction [Line Items]	'	'	'
Share exchange transaction, shares of common stock held in treasury allocated for the share exchange	'	6,350,630	'
Nidec Copal	'	'	'
Related Party Transaction [Line Items]	'	'	'
Share exchange transaction, shares of common stock held in treasury allocated for the share exchange	4,856,764	'	'
Nidec Tosok	'	'	'
Related Party Transaction [Line Items]	'	'	'
Share exchange transaction, shares of common stock held in treasury allocated for the share exchange	2,624,000	'	'
Chief Executive Officer	'	'	'
Related Party Transaction [Line Items]	'	'	'
Percentage of the outstanding shares of the Company owned by a related party	'	'	9.10%
Share exchange transaction, shares of common stock held in treasury allocated for the share exchange	589,992	306,272	'
Chief Executive Officer | Nidec Tosok	'	'	'
Related Party Transaction [Line Items]	'	'	'
Share exchange transaction, shares of common stock held in treasury allocated for the share exchange	322,400	'	'
Variable Interest Entity, Not Primary Beneficiary	'	'	'
Related Party Transaction [Line Items]	'	'	'
Percentage of the outstanding shares of the Company owned by a related party	'	'	4.00%
Immediate Family Member of Management or Principal Owner	'	'	'
Related Party Transaction [Line Items]	'	'	'
Percentage of the outstanding shares of the Company owned by a related party	'	'	1.90%
NTSC	'	'	'
Related Party Transaction [Line Items]	'	'	'
Share exchange transaction, shares of common stock held in treasury allocated for the share exchange	49,600	'	'

Leased_Assets_Under_Capital_Le

Leased Assets Under Capital Leases (Detail) (JPY ¥)	Mar. 31, 2014	Mar. 31, 2013
In Millions, unless otherwise specified
Class of property	'	'
Other leased assets	¥ 109	¥ 65
Less-Accumulated amortization	-2,511	-1,345
Capital Leases, Balance Sheet, Assets by Major Class, Net	4,934	5,670
Machinery and Equipment	'	'
Class of property	'	'
Machinery and equipment	¥ 7,336	¥ 6,950

Lease_Commitments_Additional_I

Lease Commitments - Additional Information (Detail) (JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Leases Disclosure [Line Items]	'	'	'
Amortization expenses under capital leases	¥ 1,305	¥ 524	¥ 835
Rental expenses under operating leases	2,586	2,719	1,526
Rental revenues under operating leases	¥ 175	¥ 412	¥ 373

Future_Minimum_Lease_Payments_

Future Minimum Lease Payments Under Capital Leases Together with Present Value of Net Minimum Lease Payments (Detail) (JPY ¥)	Mar. 31, 2014	Mar. 31, 2013
In Millions, unless otherwise specified
Leases Disclosure [Line Items]	'	'
2015	¥ 1,810	'
2016	2,019	'
2017	658	'
2018	563	'
2019	114	'
2020 and thereafter	9	'
Total minimum lease payments	5,173	'
Less-Amount representing interest	-312	'
Present value of net minimum lease payments	4,861	'
Less-Current obligations	-1,667	-1,540
Long-term capital lease obligations	¥ 3,194	'

Minimum_Rental_Payments_Requir

Minimum Rental Payments Required Under Operating Leases Relating Primarily to Land, Buildings and Equipment Having Initial or Remaining Non-Cancelable Lease Terms in Excess of One Year (Detail) (Noncancelable Lease Obligations, JPY ¥)	Mar. 31, 2014
In Millions, unless otherwise specified
Noncancelable Lease Obligations	'
Leases Disclosure [Line Items]	'
2015	¥ 2,319
2016	1,757
2017	1,197
2018	996
2019	965
2020 and thereafter	1,941
Total minimum future rentals	¥ 9,175

Future_Minimum_Lease_Payments_1

Future Minimum Lease Payments to be Received Under Operating Leases that have Remaining Non-Cancelable Terms (Detail) (Non Cancelable Lease Receivable, JPY ¥)	Mar. 31, 2014
In Millions, unless otherwise specified
Non Cancelable Lease Receivable	'
Leases Disclosure [Line Items]	'
2015	¥ 31
2016	25
2017	25
2018	26
2019	26
2020 and thereafter	91
Total minimum future rentals	¥ 224

Flooding_in_Thailand_Additiona

Flooding in Thailand - Additional Information (Detail) (JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Unusual or Infrequent Item [Line Items]	'	'
Net gain recognized as a result of excess insurance recovery over the flooding loss in Thailand	¥ 4,027	¥ 5,932
Thailand	'	'
Unusual or Infrequent Item [Line Items]	'	'
Recognized loss due to flooding	'	17,269
Thailand | Property Plant and Equipment	'	'
Unusual or Infrequent Item [Line Items]	'	'
Recognized loss due to flooding	'	13,730
Thailand | Inventories	'	'
Unusual or Infrequent Item [Line Items]	'	'
Recognized loss due to flooding	'	¥ 3,539

Recovered_Sheet7

Other Commitments and Contingencies, Concentrations and Factors that May Affect Future Operations - Additional Information (Detail) (JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Commitments and Contingencies Disclosure [Line Items]	'	'	'
Commitments for the purchase of property, plant and equipment and other assets	2,425	'	'
Guarantee of employees bank loans, amount	60	'	'
Guarantee of employees bank loans, maximum undiscounted amount of obligation to make future payments in the event of defaults	60	'	'
Guarantee of employees bank loans, current carrying amount	0	'	'
Accounts receivable concentration of credit risk, amount	17,706	19,534	'
ASI	'	'	'
Commitments and Contingencies Disclosure [Line Items]	'	'	'
Contingent liabilities assumed in connection with acquisition	6,967	'	'
Customer Concentration Risk | Two Largest Customers	'	'	'
Commitments and Contingencies Disclosure [Line Items]	'	'	'
Concentration of risk percentage	17.00%	20.00%	22.00%
Customer Concentration Risk | Largest Customer	'	'	'
Commitments and Contingencies Disclosure [Line Items]	'	'	'
Concentration of risk percentage	9.00%	11.00%	12.00%
Credit Concentration Risk	'	'	'
Commitments and Contingencies Disclosure [Line Items]	'	'	'
Concentration of risk percentage	10.00%	13.00%	'

Changes_in_Product_Warranty_Li

Changes in Product Warranty Liabilities (Detail) (JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Product Liability Contingency [Line Items]	'	'
Balance at beginning of year	¥ 2,201	¥ 971
Addition	2,021	1,626
Utilization	-1,080	-664
Foreign exchange impact	-106	268
Balance at end of year	¥ 3,036	¥ 2,201

Discontinued_Operations_Additi

Discontinued Operations - Additional Information (Detail) (JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'
Total exit costs, pre-tax	'	'	¥ 5,800
Total exit costs, net of tax	'	'	4,412
Goodwill impairment loss	'	'	¥ 2,045

Operating_Results_of_Discontin

Operating Results of Discontinued Operations (Detail) (JPY ¥)	3 Months Ended				12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'	'	'	'
Net sales	¥ 228,384	¥ 217,091	¥ 218,358	¥ 211,276	¥ 875,109	¥ 709,270	¥ 682,320
Loss on discontinued operations before income taxes	'	'	'	'	'	'	-7,796
Income taxes	'	'	'	'	'	'	28
Loss on discontinued operations	'	'	'	'	'	'	-7,768
Segment, Discontinued Operations	'	'	'	'	'	'	'
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'	'	'	'
Net sales	'	'	'	'	'	'	5,615
Lens Actuator Business	'	'	'	'	'	'	'
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'	'	'	'
Loss on discontinued operations before income taxes	'	'	'	'	'	'	-2,203
Income taxes	'	'	'	'	'	'	-269
Loss on discontinued operations	'	'	'	'	'	'	-2,472
Lens Actuator Business | Segment, Discontinued Operations	'	'	'	'	'	'	'
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'	'	'	'
Net sales	'	'	'	'	'	'	1,576
Nidec Pegion Business	'	'	'	'	'	'	'
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'	'	'	'
Loss on discontinued operations before income taxes	'	'	'	'	'	'	-1,817
Income taxes	'	'	'	'	'	'	129
Loss on discontinued operations	'	'	'	'	'	'	-1,688
Nidec Pegion Business | Segment, Discontinued Operations	'	'	'	'	'	'	'
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'	'	'	'
Net sales	'	'	'	'	'	'	1,365
Compact Digital Camera Lens Unit Business	'	'	'	'	'	'	'
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'	'	'	'
Loss on discontinued operations before income taxes	'	'	'	'	'	'	-3,776
Income taxes	'	'	'	'	'	'	168
Loss on discontinued operations	'	'	'	'	'	'	-3,608
Compact Digital Camera Lens Unit Business | Segment, Discontinued Operations	'	'	'	'	'	'	'
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]	'	'	'	'	'	'	'
Net sales	'	'	'	'	'	'	¥ 2,674

Product_Information_Detail

Product Information (Detail) (JPY ¥)	3 Months Ended				12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Net sales:	'	'	'	'	'	'	'
Net sales	¥ 228,384	¥ 217,091	¥ 218,358	¥ 211,276	¥ 875,109	¥ 709,270	¥ 682,320
Small Precision Motors	'	'	'	'	'	'	'
Net sales:	'	'	'	'	'	'	'
Net sales	'	'	'	'	362,513	319,724	331,437
Small Precision Motors | Hard Disk Drives Spindle Motors	'	'	'	'	'	'	'
Net sales:	'	'	'	'	'	'	'
Net sales	'	'	'	'	185,506	165,427	176,932
Small Precision Motors | Other Small Precision Motors	'	'	'	'	'	'	'
Net sales:	'	'	'	'	'	'	'
Net sales	'	'	'	'	177,007	154,297	154,505
Automotive, Appliance, Commercial and Industrial Products	'	'	'	'	'	'	'
Net sales:	'	'	'	'	'	'	'
Net sales	'	'	'	'	345,236	248,464	208,529
Machinery	'	'	'	'	'	'	'
Net sales:	'	'	'	'	'	'	'
Net sales	'	'	'	'	86,955	63,526	64,904
Electronic and Optical Components	'	'	'	'	'	'	'
Net sales:	'	'	'	'	'	'	'
Net sales	'	'	'	'	72,845	69,188	69,377
Others	'	'	'	'	'	'	'
Net sales:	'	'	'	'	'	'	'
Net sales	'	'	'	'	¥ 7,560	¥ 8,368	¥ 8,073

Revenues_from_External_Custome

Revenues from External Customers and Long-Lived Assets (Detail) (JPY ¥)	3 Months Ended				12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Net sales:	'	'	'	'	'	'	'
Net sales	¥ 228,384	¥ 217,091	¥ 218,358	¥ 211,276	¥ 875,109	¥ 709,270	¥ 682,320
Long-lived assets:	'	'	'	'	'	'	'
Long-lived assets	298,881	'	'	'	298,881	277,977	'
Japan	'	'	'	'	'	'	'
Net sales:	'	'	'	'	'	'	'
Net sales	'	'	'	'	238,278	213,169	260,470
Long-lived assets:	'	'	'	'	'	'	'
Long-lived assets	96,239	'	'	'	96,239	86,612	'
U.S.A.	'	'	'	'	'	'	'
Net sales:	'	'	'	'	'	'	'
Net sales	'	'	'	'	132,117	99,260	71,317
Long-lived assets:	'	'	'	'	'	'	'
Long-lived assets	23,046	'	'	'	23,046	21,047	'
Singapore	'	'	'	'	'	'	'
Net sales:	'	'	'	'	'	'	'
Net sales	'	'	'	'	63,950	55,712	40,595
Long-lived assets:	'	'	'	'	'	'	'
Long-lived assets	1,337	'	'	'	1,337	1,899	'
Thailand	'	'	'	'	'	'	'
Net sales:	'	'	'	'	'	'	'
Net sales	'	'	'	'	85,435	81,678	75,908
Long-lived assets:	'	'	'	'	'	'	'
Long-lived assets	37,925	'	'	'	37,925	42,418	'
The Philippines	'	'	'	'	'	'	'
Net sales:	'	'	'	'	'	'	'
Net sales	'	'	'	'	24,506	18,543	19,683
Long-lived assets:	'	'	'	'	'	'	'
Long-lived assets	12,904	'	'	'	12,904	11,838	'
China	'	'	'	'	'	'	'
Net sales:	'	'	'	'	'	'	'
Net sales	'	'	'	'	197,134	150,631	148,553
Long-lived assets:	'	'	'	'	'	'	'
Long-lived assets	65,007	'	'	'	65,007	56,756	'
Other	'	'	'	'	'	'	'
Net sales:	'	'	'	'	'	'	'
Net sales	'	'	'	'	133,689	90,277	65,794
Long-lived assets:	'	'	'	'	'	'	'
Long-lived assets	¥ 62,423	'	'	'	¥ 62,423	¥ 57,407	'

Net_Sales_to_External_Customer

Net Sales to External Customers and Other Financial Information by Operating Segments (Detail) (JPY ¥)	3 Months Ended					12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2014		Mar. 31, 2013		Mar. 31, 2012
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	¥ 228,384		¥ 217,091	¥ 218,358	¥ 211,276	¥ 875,109		¥ 709,270		¥ 682,320
Operating income	'		'	'	'	85,068		17,598		73,070
Depreciation	'		'	'	'	39,485		34,935		31,511
Total assets	1,165,918		'	'	'	1,165,918		1,005,417		'
Identifiable intangible assets and other fair value adjustments	11,626		'	'	'	11,626		12,502		'
Goodwill	154,927		'	'	'	154,927		132,775		80,525
Additions to property, plant and equipment	'		'	'	'	40,297		61,368		41,446
NCJ	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Additions to property, plant and equipment	'		'	'	'	1,884		1,991		'
Nidec Electronics (Thailand)	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Goodwill	7,645		'	'	'	7,645		6,994		6,109
Additions to property, plant and equipment	'		'	'	'	1,232		14,588		'
Nidec (Zhejiang)	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Goodwill	1,142		'	'	'	1,142		1,044		912
Additions to property, plant and equipment	'		'	'	'	712		710		'
NIDC (formerly NCD)	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Additions to property, plant and equipment	'		'	'	'	972		2,372		'
NILS (formerly NCS)	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Additions to property, plant and equipment	'		'	'	'	9		417		'
NIHC (formerly NCH)	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Additions to property, plant and equipment	'		'	'	'	6		5		'
NILF (formerly NCF)	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Additions to property, plant and equipment	'		'	'	'	3,368		1,876		'
Nidec Sankyo	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Goodwill	29,533		'	'	'	29,533		27,312		26,100
Additions to property, plant and equipment	'		'	'	'	3,712		4,777		'
Nidec Copal	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Goodwill	16,462		'	'	'	16,462		16,462		16,462
Additions to property, plant and equipment	'		'	'	'	2,427		9,539		'
Nidec Tosok	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Goodwill	1,038		'	'	'	1,038		1,038		1,107
Additions to property, plant and equipment	'		'	'	'	9,432		5,814		'
Nidec Copal Electronics	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Goodwill	6,561		'	'	'	6,561		6,561		6,561
Additions to property, plant and equipment	'		'	'	'	826		984		'
Nidec Techno Motor	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Goodwill	2,049		'	'	'	2,049		2,049		2,049
Additions to property, plant and equipment	'		'	'	'	3,549		5,144		'
Nidec Motor	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Goodwill	63,078		'	'	'	63,078		55,008		11,984
Additions to property, plant and equipment	'		'	'	'	4,134		3,594		'
Nidec Motors & Actuators	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Goodwill	7,318		'	'	'	7,318		6,385		4,737
Additions to property, plant and equipment	'		'	'	'	3,019		1,845		'
All others	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Goodwill	20,101		'	'	'	20,101		9,922		4,504
Additions to property, plant and equipment	'		'	'	'	5,015		7,712		'
Operating Segments	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	874,232		709,367		681,362
Operating income	'		'	'	'	82,880		33,574		74,829
Depreciation	'		'	'	'	44,406		38,422		32,530
Total assets	1,683,334		'	'	'	1,683,334		1,447,588		'
Operating Segments | NCJ	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	27,599		23,748		46,901
Operating income	'		'	'	'	4,865		-4,856		7,497
Depreciation	'		'	'	'	921		917		995
Total assets	628,338		'	'	'	628,338		565,451		'
Operating Segments | Nidec Electronics (Thailand)	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	67,623		63,349		64,226
Operating income	'		'	'	'	12,781		10,525		15,027
Depreciation	'		'	'	'	5,502		5,572		5,085
Total assets	116,476		'	'	'	116,476		91,784		'
Operating Segments | Nidec (Zhejiang)	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	18,017		21,109		26,430
Operating income	'		'	'	'	-243		-2,689		774
Depreciation	'		'	'	'	618		1,196		1,231
Total assets	12,112		'	'	'	12,112		13,897		'
Operating Segments | NIDC (formerly NCD)	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	1,940		3,648		4,269
Operating income	'		'	'	'	475		-409		431
Depreciation	'		'	'	'	359		914		802
Total assets	20,763		'	'	'	20,763		24,159		'
Operating Segments | NILS (formerly NCS)	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	57,893		50,039		34,220
Operating income	'		'	'	'	709		1,115		781
Depreciation	'		'	'	'	197		133		70
Total assets	27,689		'	'	'	27,689		21,590		'
Operating Segments | NIHC (formerly NCH)	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	69,890		52,028		50,748
Operating income	'		'	'	'	483		146		359
Depreciation	'		'	'	'	6		7		6
Total assets	22,458		'	'	'	22,458		15,678		'
Operating Segments | NILF (formerly NCF)	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	19,573		14,707		15,326
Operating income	'		'	'	'	6,037		4,883		7,799
Depreciation	'		'	'	'	2,732		2,750		2,598
Total assets	49,569		'	'	'	49,569		37,084		'
Operating Segments | Nidec Sankyo	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	98,564		73,201		78,589
Operating income	'		'	'	'	10,392		4,181		7,414
Depreciation	'		'	'	'	4,102		3,773		3,715
Total assets	125,929		'	'	'	125,929		107,393		'
Operating Segments | Nidec Copal	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	47,023		49,627		51,124
Operating income	'		'	'	'	-1,323		-3,192		6,384
Depreciation	'		'	'	'	4,444		3,806		3,115
Total assets	55,166		'	'	'	55,166		62,376		'
Operating Segments | Nidec Tosok	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	36,854		31,090		33,358
Operating income	'		'	'	'	3,186		1,715		3,140
Depreciation	'		'	'	'	3,775		2,930		2,660
Total assets	50,221		'	'	'	50,221		43,566		'
Operating Segments | Nidec Copal Electronics	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	31,295		26,845		29,098
Operating income	'		'	'	'	5,288		3,277		4,194
Depreciation	'		'	'	'	1,283		1,318		1,150
Total assets	42,115		'	'	'	42,115		38,684		'
Operating Segments | Nidec Techno Motor	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	50,691		39,940		40,058
Operating income	'		'	'	'	6,671		4,168		4,591
Depreciation	'		'	'	'	2,573		1,890		1,491
Total assets	49,703		'	'	'	49,703		42,508		'
Operating Segments | Nidec Motor	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	175,854		119,093		83,999
Operating income	'		'	'	'	9,314		723		2,111
Depreciation	'		'	'	'	9,171		6,481		3,892
Total assets	197,315		'	'	'	197,315		178,429		'
Operating Segments | Nidec Motors & Actuators	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	64,420		44,707		44,748
Operating income	'		'	'	'	5,334		3,447		3,126
Depreciation	'		'	'	'	2,186		1,470		1,423
Total assets	68,405		'	'	'	68,405		46,601		'
Operating Segments | All others	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	106,996		96,236		78,268
Operating income	'		'	'	'	18,911		10,540		11,201
Depreciation	'		'	'	'	6,537		5,265		4,297
Total assets	217,075		'	'	'	217,075		158,388		'
Unallocated Amount to Segment	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	877	[1]	-97	[1]	958	[1]
Operating income	'		'	'	'	2,055	[2]	-17,606	[2]	-3,072	[2]
U.S. GAAP adjustments and Others	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Operating income	'		'	'	'	-1,133	[3]	-537	[3]	-1,476	[3]
Depreciation	'		'	'	'	-4,921	[4],[5]	-3,487	[4],[5]	-1,019	[4],[5]
Total assets	-57,147	[6]	'	'	'	-57,147	[6]	-7,682	[6]	'
Business Intersegment, Eliminations	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	329,435		262,897		250,335
Operating income	'		'	'	'	1,266		2,167		2,789
Total assets	-626,822		'	'	'	-626,822		-579,766		'
Business Intersegment, Eliminations | NCJ	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	138,354		108,282		100,064
Business Intersegment, Eliminations | Nidec Electronics (Thailand)	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	43,982		35,492		36,649
Business Intersegment, Eliminations | Nidec (Zhejiang)	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	5,011		2,977		3,617
Business Intersegment, Eliminations | NIDC (formerly NCD)	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	10,559		11,117		15,471
Business Intersegment, Eliminations | NILS (formerly NCS)	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	749		709		448
Business Intersegment, Eliminations | NIHC (formerly NCH)	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	1,339		1,734		1,162
Business Intersegment, Eliminations | NILF (formerly NCF)	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	29,266		25,682		24,390
Business Intersegment, Eliminations | Nidec Sankyo	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	312		300		396
Business Intersegment, Eliminations | Nidec Copal	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	2,318		2,093		2,318
Business Intersegment, Eliminations | Nidec Tosok	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	171		190		150
Business Intersegment, Eliminations | Nidec Copal Electronics	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	11		20		20
Business Intersegment, Eliminations | Nidec Techno Motor	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	4,041		3,143		952
Business Intersegment, Eliminations | Nidec Motor	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	80		154		30
Business Intersegment, Eliminations | Nidec Motors & Actuators	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	20,213		15,170		11,607
Business Intersegment, Eliminations | All others	'		'	'	'	'		'		'
Segment Reporting Disclosure [Line Items]	'		'	'	'	'		'		'
Net sales	'		'	'	'	¥ 73,029		¥ 55,834		¥ 53,061
[1]	US GAAP adjustments primarily relate to the difference between recognition of revenue at the time of shipment and at the time of customer receipt.
[2]	Some items are reclassified from other expenses (income) and included in operating expenses (income). Main reclassification is income or loss from sales or disposals of fixed assets for the year ended March 31, 2012, 2013 and 2014.
[3]	Others is mainly from the amortization of identifiable intangible assets related to business combinations for the years ended March 31, 2012, 2013 and 2014.
[4]	Some leased assets are not capitalized in the operating segments but are capitalized under U.S. GAAP.
[5]	The amount of each segment includes amortization of intangible assets. Others mainly represent adjustments to exclude the amortization of intangible assets in order to reconcile amounts to consolidated total of depreciation in consolidated statements of cash flows.
[6]	Others is mainly due to the reclassification of deferred tax assets and liabilities on consolidation.

Segment_Information_Additional

Segment Information - Additional Information (Detail) (JPY ¥)	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
	Customer	Customer	Customer
Segment Reporting Disclosure [Line Items]	'	'	'
Number of major customers	0	1	2
Major Customer	'	'	'
Segment Reporting Disclosure [Line Items]	'	'	'
Sales to customers which exceeded 10% of the consolidated net sales	0	74,897	151,253

Subsequent_Events_Additional_I

Subsequent Events - Additional Information (Detail) (JPY ¥)	12 Months Ended	0 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 31, 2014	Apr. 02, 2014	Apr. 22, 2014	Apr. 22, 2014
		Subsequent Event	Subsequent Event	Subsequent Event
			Nidec Copal Electronics	Nidec-Read
Subsequent Event [Line Items]	'	'	'	'
Cash dividend declared	¥ 7,585	¥ 7,585	'	'
Cash dividend declared, payable date	3-Jun-14	'	'	'
Cash dividend declared, record date	31-Mar-14	'	'	'
Share exchange ratio	'	'	0.138	0.243
Number of shares allocated for share exchange	'	'	3,160,584	1,421,513

Quarterly_Financial_Data_Unaud

Quarterly Financial Data (Unaudited) (Detail) (JPY ¥)	3 Months Ended								12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2014		Mar. 31, 2013	Mar. 31, 2012
Quarterly Financial Information [Line Items]	'		'		'		'		'		'	'
Net sales	¥ 228,384		¥ 217,091		¥ 218,358		¥ 211,276		¥ 875,109		¥ 709,270	¥ 682,320
Income before income taxes	22,139		24,084		21,075		17,366		84,664		13,398	70,856
Net income attributable to Nidec Corporation	¥ 13,351		¥ 15,950		¥ 13,757		¥ 13,346		¥ 56,404		¥ 7,986	¥ 40,731
Net income attributable to Nidec Corporation per share:	'		'		'		'		'		'	'
Basic	¥ 48.41	[1]	¥ 57.84	[1]	¥ 51.26	[1]	¥ 49.73	[1]	¥ 207.31	[1]	¥ 29.64	¥ 148.12
Diluted	¥ 45.39	[1]	¥ 54.24	[1]	¥ 47.85	[1]	¥ 46.42	[1]	¥ 193.96	[1]	¥ 27.49	¥ 138.45
[1]	Earnings-per-share amounts for each quarter are computed independently. As a result, their sum may not equal the total year earnings-per-share amounts.