Accounting Policies - Additional Information (Details) (USD $)	12 Months Ended
Dec. 31, 2014 Facilities	Dec. 31, 2013	Dec. 31, 2012
Accounting Policies [Abstract]
Research and development expense	$ 23,149,000us-gaap_ResearchAndDevelopmentExpense	$ 24,075,000us-gaap_ResearchAndDevelopmentExpense	$ 23,851,000us-gaap_ResearchAndDevelopmentExpense
Advertising expense	13,463,000us-gaap_AdvertisingExpense	15,026,000us-gaap_AdvertisingExpense	16,401,000us-gaap_AdvertisingExpense
Number of subsidiaries	2
Unremitted earnings of foreign subsidiaries	$ 41,400,000
Convertible Subordinated Debt
Debt Conversion [Line Items]
Initial conversion price	$ 24.79

The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

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Amount of undistributed earnings of foreign subsidiaries intended to be permanently reinvested outside the country of domicile.

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