Borrowings - Components of Long-Term Debt (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended		0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Jun. 13, 2011	Dec. 31, 2012	Aug. 09, 2010
Line Of Credit Facility [Line Items]
Long-term debt, Gross	$ 1,104,598	$ 1,334,700
Less: Unamortized debt discount on 3.875% Convertible Senior Subordinated Notes due 2017	(36,197)	(48,413)
Total long-term debt	1,068,401	1,286,287
Debt, Current	368,401	356,287
Long-term borrowings	700,000	930,000
Interest rate	3.875%	3.875%		3.875%
Revolving Credit Facility
Line Of Credit Facility [Line Items]
Revolving credit facility, at a rate of 1.92% at December 31, 2014 and 2013, due July 16, 2018	200,000	680,000
Senior credit facility interest rate	1.92%	1.92%
Debt maturity date	Jul. 16, 2018
3.875% Convertible Senior Subordinated Notes
Line Of Credit Facility [Line Items]
3.875% Convertible Senior Subordinated Notes due 2017	399,898	400,000			400,000
Interest rate	3.875%	3.875%			3.875%
6.875% Senior Subordinated Notes Due 2019
Line Of Credit Facility [Line Items]
6.875% Senior Subordinated Notes due 2019	250,000	250,000	250,000
Interest rate	6.875%	6.875%	6.875%
Debt instrument maturity date	2019	2019	2019
5.25% Senior Subordinated Notes Due 2024
Line Of Credit Facility [Line Items]
5.25% Senior Notes due 2024	250,000	0
Interest rate	5.25%	5.25%
Securitization Program
Line Of Credit Facility [Line Items]
Other Short-term Borrowings	$ 4,700	$ 4,700
Interest rate	0.92%	0.92%