Debt Obligations (Details) (USD $)	12 Months Ended				9 Months Ended	12 Months Ended													12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 1.625% Issue [Member]	Oct. 15, 2012 3.5% Issue [Member]	Dec. 31, 2012 3.5% Issue [Member]	Dec. 31, 2011 3.5% Issue [Member]	Dec. 31, 2010 3.5% Issue [Member]	Oct. 04, 2005 3.5% Issue [Member]	Dec. 31, 2012 Term Loan [Member]	Dec. 31, 2011 Term Loan [Member]	Aug. 18, 2011 Term Loan [Member]	Dec. 31, 2012 3.5% Issue [Member]	Dec. 31, 2011 3.5% Issue [Member]	Dec. 31, 2012 Line of Credit [Member]	Dec. 31, 2011 Line of Credit [Member]	Dec. 31, 2011 Line of credit - India [Member]	Dec. 31, 2012 Loans Payable [Member]	Dec. 31, 2011 Credit facility [Member]	Dec. 31, 2012 Revolving Credit Facility [Member]	Oct. 11, 2012 Revolving Credit Facility [Member]	Dec. 31, 2011 Revolving Credit Facility [Member]	Aug. 18, 2011 Revolving Credit Facility [Member]	Dec. 31, 2012 Minimum [Member]	Dec. 31, 2012 Maximum [Member]	Dec. 31, 2012 Letter of Credit [Member] Line of Credit [Member]	Dec. 31, 2012 Swingline loans [Member] Line of Credit [Member]	Dec. 31, 2012 LIBOR [Member] Minimum [Member]	Dec. 31, 2012 LIBOR [Member] Maximum [Member]	Dec. 31, 2012 Base rate [Member] Minimum [Member]	Dec. 31, 2012 Base rate [Member] Maximum [Member]	Aug. 18, 2011 Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Convertible, Conversion Price							$ 40.48
Debt Instrument, Interest Rate at Period End																		2.00%
Debt Instrument, Interest Rate Terms	The base rate is the highest of (i) the Bank of America prime rate, (ii) the Federal Funds rate plus 0.50% or (iii) the Fixed LIBOR rate plus 1.00%.
Debt Instrument, Basis Spread on Variable Rate																												1.50%	2.50%	0.50%	1.50%
Extinguishment of Debt, Amount				$ 3,600,000		$ 167,900,000
Debt Instrument, Face Amount						3,600,000	171,400,000		175,000,000
Total Debt [Roll Forward]
Short-term Debt	(1,050,000)	(981,000)
Convertible Debt													3,586,000	165,173,000
Line of Credit Facility, Amount Outstanding																				215,117,000		87,194,000
Loans Payable to Bank										74,500,000	79,000,000	80,000,000
Amortization of Debt Discount (Premium)						6,300,000	7,600,000	7,100,000
Capital Lease Obligations, Current	(2,397,000)	(2,178,000)
Capital Lease Obligations, Noncurrent	4,589,000	4,249,000
Long-term Debt, Current Maturities	(6,500,000)	(169,673,000)
Long-term Debt	293,203,000	331,367,000
Debt Instrument, Face Amount						3,600,000	171,400,000		175,000,000
Debt Instrument, Unamortized Discount						0	6,300,000
Long-term Debt, Fair Value	286,703,000	161,694,000
Gains (Losses) on Extinguishment of Debt	0	(1,899,000)	0	200,000															1,700,000
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months	6,500,000
Long-term Debt, Maturities, Repayments of Principal in Year Two	8,500,000
Long-term Debt, Maturities, Repayments of Principal in Year Three	15,100,000
Long-term Debt, Maturities, Repayments of Principal in Year Four	263,100,000
Long-term Debt, Maturities, Repayments of Principal in Year Five	0
Letters of Credit Outstanding, Amount	113,400,000														47,500,000	35,300,000
Line of Credit Facility, Maximum Borrowing Capacity		355,000,000															10,000,000					265,000,000				200,000,000	25,000,000
Deferred Finance Costs, Noncurrent, Gross	5,500,000								5,100,000
Incremental Credit Facility Option																				80,000,000		205,000,000
Line of Credit Facility, Maximum Borrowing Capacity, Pre-modification																					275,000,000		100,000,000
Term Loan, Maximum Borrowing Capacity, Pre-modification																																126,000,000
Line of Credit Facility, Current Borrowing Capacity																				400,000,000
Consolidated Total Leverage Ratio																									4.0
Consolidated Senior Secured Leverage Ratio																									3.0
Consolidated Fixed Charge Coverage Ratio																								1.5
Short-term Debt, Weighted Average Interest Rate	6.70%	7.30%
Debt Instrument, Convertible, Effective Interest Rate					8.40%		8.40%	8.40%
Debt Instrument, Convertible, Interest Expense						$ 4,800,000	$ 6,100,000	$ 6,100,000
Debt Instrument, Interest Rate, Stated Percentage									3.50%
Debt Instrument, Interest Rate, Stated Percentage									3.50%
Debt Instrument, Interest Rate, Stated Percentage									3.50%
Letter of credit, interest rate at period end	1.75%	2.00%
Line of Credit Facility, Interest Rate at Period End	2.50%