Basis of Presentation (Details 3) (USD $) Share data in Millions, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Stock-based compensation activity, including both continuing and discontinued operations
Stock-based compensation expense recognized in operating expenses	$ 2,807,000	$ 2,052,000	$ 5,686,000	$ 5,120,000
Tax benefit of stock-based compensation expense in provision for income taxes	896,000	705,000	1,944,000	1,771,000
Stock-based compensation expense, net of tax	1,911,000	1,347,000	3,742,000	3,349,000
Fair value of shares vested	2,836,000	1,895,000	5,649,000	5,005,000
Proceeds to the Company from the exercise of stock-based compensation	280,000	225,000	776,000	1,983,000
Tax effect from exercise of stock-based compensation, including (shortfall) tax benefits	(7,000)	(54,000)	(1,850,000)	(56,000)
Stock-based compensation cost capitalized in inventory			384,000	229,000
Fair value of financial instruments
United States Treasury securities and money market funds included in cash equivalents	60,725,000	51,283,000	60,725,000	51,283,000	76,130,000
Income Taxes
Non-deductible acquisition costs					2,300,000
Effective tax rate (as a percent)	37.70%	41.70%	39.80%	43.50%
Provision for income taxes	$ 11,177,000	$ 11,347,000	$ 15,434,000	$ 17,719,000
1994 Plan
Stock-Based Compensation
Requisite service period for options to vest			4 years
Expiration period for options granted			7 years
Age after which vesting of options granted accelerates if the grantee ceases to be employed by the entity			60 years
2011 Plan
Stock-Based Compensation
Maximum common stock shares that may be issued under plan	16.3		16.3