Debt and Commitments (Details Narrative) (USD $)	12 Months Ended					12 Months Ended		0 Months Ended			12 Months Ended				12 Months Ended				12 Months Ended			12 Months Ended		12 Months Ended
	Dec. 31, 2012 months	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Bank Overdrafts [Member]	Dec. 31, 2011 Bank Overdrafts [Member]	Dec. 31, 2012 Line of Credit [Member]	Dec. 31, 2011 Line of Credit [Member]	Apr. 05, 2011 Convertible Debt [Member] 3.75% Convertible Notes [Member]	Apr. 05, 2011 Convertible Debt [Member] 3.75% Convertible Notes [Member] Redeemed With Accrued Interest [Member]	Apr. 05, 2011 Convertible Debt [Member] 3.75% Convertible Notes [Member] Surrendered For Conversion [Member]	Dec. 31, 2012 Convertible Debt [Member] 3.375% Convertible Notes [Member] D	Dec. 31, 2009 Convertible Debt [Member] 3.375% Convertible Notes [Member]	Dec. 31, 2011 Convertible Debt [Member] 3.375% Convertible Notes [Member]	Dec. 31, 2007 Convertible Debt [Member] 3.375% Convertible Notes [Member]	Dec. 31, 2012 Revolving Credit Agreement [Member]	Dec. 31, 2011 Revolving Credit Agreement [Member]	Jul. 10, 2012 Revolving Credit Agreement [Member]	Sep. 26, 2011 Revolving Credit Agreement [Member]	Dec. 31, 2012 Bank Overdrafts [Member]	Dec. 31, 2012 Minimum [Member]	Dec. 31, 2012 Minimum [Member] Revolving Credit Agreement [Member]	Dec. 31, 2012 Maximum [Member]	Dec. 31, 2012 Maximum [Member] Revolving Credit Agreement [Member]	Dec. 31, 2012 On Or Before September 30 2013 [Member] Minimum [Member] Revolving Credit Agreement [Member]	Dec. 31, 2012 On Or Before September 30 2013 [Member] Maximum [Member] Revolving Credit Agreement [Member]	Dec. 31, 2012 After September 30 2013 [Member] Minimum [Member] Revolving Credit Agreement [Member]	Dec. 31, 2012 After September 30 2013 [Member] Maximum [Member] Revolving Credit Agreement [Member]
Debt Instrument [Line Items]
Debt instrument, face amount														$ 100,000,000
Deferred tax assets, noncurrent, operating loss carryforwards, reduction for convertible notes redemption								15,252,000
Convertible notes stated interest rate								3.75%			3.375%
Convertible note repurchases, par value												44,364,000
Debt instrument, convertible, conversion ratio											35.3235
Debt instrument, convertible, conversion price											$ 28.31
Number of days used to calculate highest average stock price											20
Total pool of days used to calculate the highest average stock price											30
Minimum ratio of stock price to conversion price for conversion											130.00%
Guaranteed cash payment upon conversion per note											1
Debt instrument, convertible, eligible for conversion	0	0
Convertible notes								92,500,000	11,865,000	80,635,000	55,636,000		55,636,000		589,200,000	281,900,000
Repayments of convertible debt, including premium on conversion								90,438,000
Premium paid on convertible debt redemption	0	9,803,000	0					9,803,000
Adjustments to additional paid in capital, premium paid on convertible debt redemption								6,085,000
Adjustments to additional paid in capital, income tax benefit from premium paid on convertible debt redemption, tax								3,718,000
Contingent convertible debt interest, amount recaptured for income tax purpose								40,217,000
Reduction in short-term deferred tax liabilities								15,252,000
Amortization period	15
Debt instrument, convertible, effective interest rate											8.00%
Line of credit facility maximum borrowing capacity						15,000,000									750,000,000	500,000,000		400,000,000
Line of credit expiration date extension																4 years
Line of Credit Facility, Accordian Feature Amount																	250,000,000
Payments of debt issue costs															1,030,000	2,012,000
Debt instrument basis spread on LIBOR																					1.10%		1.70%
Line of credit facility, amount outstanding															589,200,000
Line of credit facility remaining borrowing capacity															160,800,000
Line of credit facility, interest rate at period end						2.16%	2.17%								1.97%	1.49%
Debt covenant ratio of senior debt to EBITDA																									3.25		3.00
Debt covenant ratio of total debt to EBITDA																									4.00		3.75
Debt covenant ratio of EBITDA to cash interest expense																								4.25		4.50
Notes and overdrafts payable	3,795,000	12,364,000		580,000	364,000	2,800,000	12,000,000
Repayment period						7 days													2 days
Maturity of Bank Acceptances																				3 months		6 months
Letters of credit outstanding, amount	$ 6,319,000