Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Jan. 31, 2012	Jan. 31, 2011	Jan. 31, 2010
Revenues:
System and software	$ 631,549	$ 562,355	$ 479,493
Service and support	383,089	352,398	323,234
Total revenues	1,014,638	914,753	802,727
Cost of revenues:
System and software	54,972	42,865	33,835
Service and support	108,690	99,612	88,704
Amortization of purchased technology	9,796	13,771	12,012
Total cost of revenues	173,458	156,248	134,551
Gross margin	841,180	758,505	668,176
Operating expenses:
Research and development	310,758	296,631	264,051
Marketing and selling	326,608	312,834	297,718
General and administration	74,811	80,948	75,056
Equity in earnings of Frontline	(2,268)	(2,051)
Amortization of intangible assets	5,905	7,347	11,184
Special charges	13,174	10,257	21,334
Total operating expenses	728,988	705,966	669,343
Operating income (loss)	112,192	52,539	(1,167)
Other income (expense), net	1,576	(2,116)	(928)
Interest expense	(31,444)	(18,411)	(17,546)
Income (loss) before income tax	82,324	32,012	(19,641)
Income tax expense (benefit)	(1,063)	3,428	2,248
Net income (loss)	83,387	28,584	(21,889)
Less: Loss attributable to noncontrolling interest	(485)
Net income (loss) attributable to Mentor Graphics shareholders	$ 83,872	$ 28,584	$ (21,889)
Net income (loss) per share attributable to Mentor Graphics shareholders:
Basic	$ 0.76	$ 0.27	$ (0.23)
Diluted	$ 0.74	$ 0.26	$ (0.23)
Weighted average number of shares outstanding:
Basic	110,138	107,743	96,474
Diluted	112,915	109,861	96,474