Debt (Long Term Debt Instruments) (Parenthetical) (Detail)	Sep. 30, 2013 Senior Notes [Member] 4.875% Senior Notes [Member] Unsecured Debt [Member]	Dec. 31, 2012 Senior Notes [Member] 7.625% Senior Notes [Member] Unsecured Debt [Member]	Sep. 30, 2013 Convertible Debt [Member] 2011 4.0% Notes [Member] Unsecured Debt [Member]	Sep. 30, 2013 Convertible Debt [Member] 2011 4.25% Notes [Member] Unsecured Debt [Member]	Sep. 30, 2013 Convertible Debt [Member] 2009 4.0% Notes [Member] Unsecured Debt [Member]	Sep. 30, 2013 Convertible Debt [Member] 2009 4.25% Notes [Member] Unsecured Debt [Member]	Sep. 30, 2013 Capital Lease Obligations [Member]	Sep. 30, 2013 Loans Payable [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate	4.875%	7.625%	4.00%	4.25%	4.00%	4.25%
Debt instrument, weighted average interest rate							2.80%	3.50%