Note 3 - Acquisitions (Detail) (USD $)	3 Months Ended			12 Months Ended			12 Months Ended		3 Months Ended	12 Months Ended				3 Months Ended
	Mar. 31, 2011	Dec. 31, 2011 Accrued [Member] MES Group [Member]	Dec. 31, 2011 Accrued [Member] Other 2011 Acquisitions [Member]	Dec. 31, 2011 MES Group [Member]	Mar. 31, 2011 MES Group [Member]	Feb. 28, 2011 MES Group [Member]	Dec. 31, 2011 Premex Group [Member]	Mar. 31, 2012 Premex Group [Member]	Mar. 31, 2012 Other 2011 Acquisitions [Member]	Dec. 31, 2011 Other 2011 Acquisitions [Member]	Dec. 31, 2010 Other 2011 Acquisitions [Member]	Dec. 31, 2009 National IME Centres Inc. [Member]	Dec. 31, 2009 MLS Group of Companies Inc. [Member]	Mar. 31, 2011 Additional Interest Expense [Member]	Mar. 31, 2011 Incremental Depreciation [Member]	Mar. 31, 2011 Selling, General and Administrative Expenses [Member]
Business Acquisition, Percentage of Voting Interests Acquired				100.00%			100.00%					100.00%	100.00%
Business Acquisition, Cost of Acquired Entity, Purchase Price				$ 215,000,000			$ 108,400,000			$ 45,100,000
Business Acquisition, Cost of Acquired Entity, Cash Paid				175,000,000			66,500,000			43,700,000
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares (in Shares)				1,424,501			661,610			214,926
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned				30,000,000			15,100,000			2,000,000
Closing Price Per Share (in Dollars per share)						$ 21.07	$ 22.85
Business Acquisition, Purchase Price Allocation, Liabilities Assumed						10,000,000	26,800,000
Business Acquisition, Cost of Acquired Entity, Transaction Costs		2,000,000	630,000		439,000		646,000	19,000		21,000	4,000
Business Acquisition, Purchase Price Allocation, Current Assets, Cash and Cash Equivalents										564,000
Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Consideration Transferred									908,000
Business Acquisition, Purchase Price Allocation, Goodwill, Expected Tax Deductible Amount										18,800,000
Business Acquisition Purchase Price Allocation Intangible Assets Expected Tax Deductible Amount										20,800,000
Business Acquisition, Pro Forma Revenue	121,300,000
Business Acquisition, Pro Forma Net Income (Loss)	(157,000)
Business Acquisition Proforma Adjustments														$ 3,300,000	$ 5,800,000	$ 5,200,000