Debt (Long Term Debt Instruments) (Detail) (USD $)			6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2013 Line of Credit [Member] Revolving Credit Facility [Member]	Dec. 31, 2012 Line of Credit [Member] Revolving Credit Facility [Member]	Jun. 30, 2013 Convertible Debt [Member] New 4.0% Notes [Member]	Dec. 31, 2012 Convertible Debt [Member] New 4.0% Notes [Member]	Jun. 30, 2013 Convertible Debt [Member] New 4.25% Notes [Member]	Dec. 31, 2012 Convertible Debt [Member] New 4.25% Notes [Member]	Jun. 30, 2013 Convertible Debt [Member] Original 4.0% Notes [Member]	Dec. 31, 2012 Convertible Debt [Member] Original 4.0% Notes [Member]	Jun. 30, 2013 Convertible Debt [Member] Original 4.25% Notes [Member]	Dec. 31, 2012 Convertible Debt [Member] Original 4.25% Notes [Member]	Jun. 30, 2013 Capital Lease Obligations [Member]	Dec. 31, 2012 Capital Lease Obligations [Member]	Jun. 30, 2013 Loans Payable [Member]	Dec. 31, 2012 Loans Payable [Member]	Jun. 30, 2013 Unsecured Debt [Member] Senior Notes [Member] 4.875% Senior Notes [Member]	Dec. 31, 2012 Unsecured Debt [Member] Senior Notes [Member] 4.875% Senior Notes [Member]	Dec. 31, 2012 Unsecured Debt [Member] Senior Notes [Member] 7.625% Senior Notes [Member]	Jun. 30, 2013 Unsecured Debt [Member] Senior Notes [Member] 7.625% Senior Notes [Member]
Debt Instrument [Line Items]
Line of credit facility, expiration date			Aug. 22, 2016
Debt instrument, maturity date					Jun. 15, 2014		Dec. 15, 2014		Jun. 15, 2014		Dec. 15, 2014				May 31, 2018		Mar. 15, 2023		Feb. 01, 2017
Lease expiration date													Mar. 31, 2020
Credit facility, amount outstanding			$ 70,600,000	$ 134,000,000
Carrying value of debt					102,300,000	100,900,000	93,300,000	92,100,000	9,600,000	9,700,000	3,000,000	3,000,000			59,200,000	30,200,000	400,000,000	0	150,000,000	0
Capital lease obligations													118,400,000	79,000,000
Total debt	856,400,000	598,900,000
Less current maturities	(49,907,000)	(52,596,000)
Long-term debt	$ 806,497,000	$ 546,323,000