Basis of Presentation (Details 2) (USD $) Share data in Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Stock option activity, including both continuing and discontinued operations
Stock option expense recognized in operating expenses	$ 845,000	$ 218,000	$ 2,293,000	$ 585,000
Tax benefit of stock option expense in provision for income tax	297,000	56,000	818,000	173,000
Stock option expense, net of tax	548,000	162,000	1,475,000	412,000
Fair value of shares vested	837,000	179,000	2,118,000	561,000
Proceeds to the Company from the exercise of stock options		863,000	154,000	955,000
Tax effect from exercise of stock options, including shortfall tax benefits		(9,000)	(39,000)	(83,000)
Stock option cost capitalized in inventory			108,000	44,000
Fair value of financial instruments
United States Treasury securities and money market funds included in cash equivalents	171,600,000		171,600,000
Income Taxes
Effective tax rate (as a percent)	37.60%	37.80%	39.00%	39.20%
Provision for income taxes	$ 11,754,000	$ 12,773,000	$ 17,016,000	$ 19,903,000
1994 Plan
Stock-Based Compensation
Number of grants generally made annually under stock option plans			Once
Requisite service period for options to vest (in years)			4
Expiration period for options granted (in years)			7
Age after which vesting of options granted accelerates if the grantee ceases to be employed by the entity (in years)			60
1995 Plan
Stock-Based Compensation
Number of grants generally made annually under stock option plans			Once
2011 Plan
Stock-Based Compensation
Maximum common stock shares that may be sold under plan (in shares)	16.3		16.3