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Interest rate stated in the contractual debt agreement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount borrowed under the credit facility as of the balance sheet date.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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Debt (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended										9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011 On Or Before September 30 2013 [Member] Minimum [Member]	Sep. 30, 2011 On Or Before September 30 2013 [Member] Maximum [Member]	Sep. 30, 2011 After September 30 2013 [Member] Minimum [Member]	Sep. 30, 2011 After September 30 2013 [Member] Maximum [Member]	Sep. 30, 2011 Minimum [Member]	Sep. 30, 2011 Maximum [Member]	Apr. 05, 2011 Redeemed With Accrued Interest [Member] Convertible Debt [Member] 3.75% Convertible Notes [Member]	Apr. 05, 2011 Surrendered For Conversion [Member] Convertible Debt [Member] 3.75% Convertible Notes [Member]	Sep. 30, 2011 Convertible Debt [Member] 3.75% Convertible Notes [Member]	Apr. 05, 2011 Convertible Debt [Member] 3.75% Convertible Notes [Member]	Sep. 30, 2011 Convertible Debt [Member] 3.375% Convertible Notes [Member]
Debt Instrument [Line Items]
Line of credit facility previous maximum borrowing capacity	$ 400,000
Line of credit facility, maximum borrowing capacity	500,000
Line of credit expiration date extension	4 years
Line of credit facility, amount outstanding	286,100
Line of credit facility remaining borrowing capacity	213,900
Debt instrument basis spread on LIBOR							1.10%	1.70%
Debt covenant ratio of senior debt to EBITDA				3.25		3
Debt covenant ratio of total debt to EBITDA				4		3.75
Debt covenant ratio of EBITDA to cash interest expense			4.25		4.50
Payments for Fees	1,927
Convertible notes remaining principal amount									11,865	80,635		92,500
Convertible notes stated interest rate											3.75%		3.375%
Repayments of convertible debt, including premium on conversion											90,438
Premium paid on convertible debt redemption	9,803	0									9,803
Adjustments to additional paid in capital, premium paid on convertible debt redemption											6,085
Adjustments to additional paid in capital, income tax benefit from premium paid on convertible debt redemption											3,718
Contingent convertible debt interest, amount recaptured for income tax purpose											40,217
Reduction in short-term deferred tax liabilities											15,252
Deferred Tax Assets, Noncurrent, Operating Loss Carryforwards, Reduction for Convertible Notes Redemption											$ 15,252