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Net Income Per Common Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended	3 Months Ended		6 Months Ended				1 Months Ended		6 Months Ended			6 Months Ended	3 Months Ended		6 Months Ended
	Feb. 28, 2011	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	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]	Feb. 28, 2011 Restricted Stock Units (RSUs) [Member]	Feb. 28, 2011 Performance Share Awards [Member]	Jun. 30, 2011 Performance Share Awards [Member]	Jun. 30, 2011 Convertible Debt [Member] 3.75% Convertible Notes [Member]	Apr. 05, 2011 Convertible Debt [Member] 3.75% Convertible Notes [Member]	Jun. 30, 2011 Convertible Debt [Member] 3.375% Convertible Notes [Member]	Jun. 30, 2011 3.75% and 3.375% Convertible Notes [Member]	Jun. 30, 2010 3.75% and 3.375% Convertible Notes [Member]	Jun. 30, 2011 3.75% and 3.375% Convertible Notes [Member]	Jun. 30, 2010 3.75% and 3.375% Convertible Notes [Member]
Net Income Per Common Share
Weighted Average Number Diluted Shares Outstanding Adjustment		874,100	792,801	881,019	682,232
Adjustments to net income for the purposes of computing income available to common stockholders		$ 0	$ 0	$ 0	$ 0
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		702,958	1,561,000	923,821	1,783,628
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	379,900
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period								109,989	79,500
Minimum Range of Target Award of Stock Plan										0.00%
Maximum Range of Target Award of Stock Plan										250.00%
Convertible notes stated interest rate											3.75%		3.375%
Convertible Debt, Maturity Date											2025-08		2027-03
Convertible notes remaining principal amount						11,865	80,635					92,500
Repayments of convertible debt, including premium on conversion											90,438
Premium paid on convertible debt redemption		9,803		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
Deferred Tax Assets, Noncurrent, Operating Loss Carryforwards, Reduction for Convertible Notes Redemption											15,252
Reduction in short-term deferred tax liabilities											$ 15,252
Debt Instrument, Convertible, Conversion Price													$ 28.31
Trading Days Used To Compute Average Closing Price of Stock for Dilutive Effect Comparison				30D
Incremental Common Shares Attributable to Conversion of Debt Securities														0	0	0	0