Debt (Schedule of Long Term Debt Instruments) (Parenthetical) (Detail)	Dec. 31, 2013 Capital Lease Obligations [Member]	Dec. 31, 2013 Machinery and Equipment [Member] Equipment Notes Payable [Member]	Dec. 31, 2013 Unsecured Debt [Member] 4.875% Senior Notes [Member] Senior Notes [Member]	Dec. 31, 2012 Unsecured Debt [Member] 7.625% Senior Notes [Member] Senior Notes [Member]	Dec. 31, 2013 Unsecured Debt [Member] 2011 4.0% Notes [Member] Convertible Debt [Member]	Dec. 31, 2013 Unsecured Debt [Member] 2011 4.25% Notes [Member] Convertible Debt [Member]	Dec. 31, 2013 Unsecured Debt [Member] 2009 4.0% Notes [Member] Convertible Debt [Member]	Dec. 31, 2013 Unsecured Debt [Member] 2009 4.25% Notes [Member] Convertible Debt [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	2.70%	3.20%