Leases (Details) (USD $)	12 Months Ended
	Dec. 31, 2012 sqft	Dec. 31, 2011	Dec. 31, 2010
Canonsburg Office | Amended Lease Agreement Effective January 1, 2004
Operating Leased Assets [Line Items]
Area of Real Estate Property	107,000
Lease rental expense incurred	$ 1,300,000	$ 1,300,000	$ 1,300,000
Future minimum lease payments, 2013	1,400,000
Future minimum lease payments, 2014	1,400,000
Canonsburg Office, New Company Headquarters | Lease Agreement Effective September 14, 2012
Operating Leased Assets [Line Items]
Area of Real Estate Property	186,000
Period of leased property (years)	183 months
Base rent, years one through five	4,300,000
Base rent, years six through ten	4,500,000
Base rent, years eleven through fifteen	4,700,000
Pittsburgh Office
Operating Leased Assets [Line Items]
Future minimum lease payments, 2014	570,000,000
Global Office Space
Operating Leased Assets [Line Items]
Lease rental expense incurred	13,700,000	12,800,000	11,500,000
Future minimum lease payments, 2013	12,600,000
Future minimum lease payments, 2014	10,700,000
Future minimum lease payments, 2015	10,000,000
Future minimum lease payments, 2016	8,200,000
Future minimum lease payments, 2017	7,400,000
Apache Design Solutions, Inc. | San Jose Office [Member]
Operating Leased Assets [Line Items]
Area of Real Estate Property	52,000
Future minimum lease payments	9,200,000
Future minimum lease payments, 2013	$ 900,000