Income taxes (Details 2) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2011	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income tax reconciliation
Statutory U.S. federal income tax rate			$ 7,246,000	$ 25,339,000	$ 14,007,000
State taxes, net			1,848,000	2,903,000	1,574,000
Foreign rate differential			6,269,000	(1,299,000)	(1,401,000)
Valuation allowance - foreign losses			(1,907,000)	3,874,000	2,861,000
Italy step-up amortization			(2,421,000)	(2,607,000)	(2,573,000)
Domestic manufacturing deduction			(1,416,000)	(1,944,000)	(839,000)
Settlement of U.S. Government resolutions	46,000,000		9,520,000
Other items, net			2,637,000	1,924,000	1,920,000
Total tax expense			21,776,000	28,190,000	15,549,000
Income tax rate reconciliation
Statutory U.S. federal income tax rate (as a percent)			35.00%	35.00%	35.00%
State taxes, net (as a percent)			8.90%	4.00%	3.90%
Foreign rate differential (as a percent)			30.30%	(1.80%)	(3.50%)
Valuation allowance - foreign losses (as a percent)			(9.20%)	5.40%	7.20%
Italy step-up amortization (as a percent)			(11.70%)	(3.60%)	(6.40%)
Domestic manufacturing deduction (as a percent)			(6.80%)	(2.70%)	(2.10%)
Settlement of U.S. Government resolutions (as a percent)			46.00%	0.00%	0.00%
Other items, net (as a percent)			12.70%	2.60%	4.80%
Income tax effective rate (as a percent)			105.20%	38.90%	38.90%
Income tax effective rate excluding the impact of the charges related to the U.S. Government resolutions (as a percent)			38.10%
Net gain on sale of vascular operations		12,019,000		12,019,000
Unrecognized tax benefits
Gross unrecognized tax benefit			700,000	600,000
Accrued interest and penalties related to unrecognized tax benefits			500,000	400,000
Reconciliation of gross unrecognized tax benefits (excluding interest)
Balance at the beginning of period	569,000	442,000	569,000	442,000
Additions for current year tax positions			162,000	70,000
Decreases (increases) for prior year tax positions			(17,000)	57,000
Expiration of statutes			(28,000)
Balance at the end of period			686,000	569,000	442,000
Unremitted earnings of foreign subsidiaries on which income tax expense is not provided			$ 301,800,000