RETIREMENT PLAN AND POST-RETIREMENT BENEFITS, Plan Changes (Details) (USD $)	12 Months Ended				12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2012 Amendment to Cap Company Contributions [Member] Supplemental Executive Retirement and Restoration Plans [Member]	Dec. 31, 2009 Amendment to Cap Company Contributions [Member] Supplemental Executive Retirement and Restoration Plans [Member]	Dec. 31, 2012 Voluntary lump sum payout member [Member] United States Pension Plans of US Entity, Defined Benefit [Member]	Dec. 31, 2013 Voluntary lump sum payout member [Member] United States Pension Plans of US Entity, Defined Benefit [Member]
Compensation and Retirement Disclosure [Abstract]
Vesting period under cash balance formula (in years)	three years
Defined Benefit Plan Amendments [Line Items]
Plan changes, description					NVE also has a non-qualified Supplemental Executive Retirement Plan and a Restoration Plan for executives. NVE contributed $26.5 million to establish a rabbi trust for these plans in 2009. See Note 4, Investments in Subsidiaries and Other Property, for details regarding the trust assets. NVE’s obligation under these supplemental and restoration plans is included in “Accrued retirement benefits” in NVE’s consolidated balance sheet, and amounted to $36.1 million at December 31, 2012. NVE is not required to make contributions to the plans.		In 2012, NVE offered a voluntary lump sum pension payout to former employees not currently of retirement age but eligible for future benefits and certain retiree participants already receiving benefits under NVE’s pension plan in an effort to reduce NVE’s future pension obligation. The 2012 payouts, as indicated in the benefits obligations table below, increased benefits paid by approximately $28.9 million. Of the offers still outstanding at December 31, 2012, NVE expects to payout an additional lump sum of approximately $15.6 million from the pension assets during 2013.
Effect of plan amendment on projected benefit obligation							$ 28,900,000	$ 15,600,000
Plan contributions						26,500,000
Trust assets	$ 32,519,000	[1]	$ 29,182,000	[1]	$ 36,100,000

[1] Rabbi Trust assets represent non-qualified deferred compensation and certain defined benefit plans, which consist of actively traded money market and equity funds with quoted prices in active markets which are considered level 1 in the fair value hierarchy. The balance also includes life insurance policies, which are recorded at the cash surrender value of $19.9 million and $13.5 million at December 31, 2012 and 2011, respectively.