Condensed Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jul. 31, 2012	Jul. 31, 2011	Jul. 31, 2012	Jul. 31, 2011
Revenues:
System and software	$ 139,957	$ 117,495	$ 289,313	$ 257,140
Service and support	100,854	96,245	199,416	186,635
Total revenues	240,811	213,740	488,729	443,775
Cost of revenues:
System and software	15,292	14,294	30,082	30,371
Service and support	29,130	26,844	57,544	52,055
Amortization of purchased technology	2,154	2,754	4,333	6,111
Total cost of revenues	46,576	43,892	91,959	88,537
Gross margin	194,235	169,848	396,770	355,238
Operating expenses:
Research and development	72,951	69,905	143,997	139,273
Marketing and selling	79,068	75,758	158,820	153,682
General and administration	19,865	17,348	36,514	34,133
Equity in earnings of Frontline	(662)	(1,139)	(1,249)	(2,156)
Amortization of intangible assets	1,599	1,455	3,305	3,065
Special charges	1,507	1,677	2,654	6,224
Total operating expenses	174,328	165,004	344,041	334,221
Operating income	19,907	4,844	52,729	21,017
Other income (expense), net	(379)	529	(296)	54
Interest expense	(4,737)	(4,634)	(9,331)	(22,074)
Income (loss) before income tax	14,791	739	43,102	(1,003)
Income tax expense (benefit)	(2,764)	(3,595)	(1,983)	(2,984)
Net income (loss)	17,555	4,334	45,085	1,981
Less: Loss attributable to noncontrolling interest	(612)	0	(1,264)	0
Net income (loss) attributable to Mentor Graphics shareholders	$ 18,167	$ 4,334	$ 46,349	$ 1,981
Net income (loss) per share:
Basic (in dollars per share)	$ 0.17	$ 0.04	$ 0.42	$ 0.02
Diluted (in dollars per share)	$ 0.16	$ 0.04	$ 0.41	$ 0.02
Weighted average number of shares outstanding:
Basic (in shares)	109,875	110,027	109,891	110,888
Diluted (in shares)	113,046	112,844	113,078	113,892