Debt (Schedule Of Convertible Notes, Carrying Amount Details) (Detail) (Convertible Debt [Member], USD $)	Mar. 31, 2013		Dec. 31, 2012	Mar. 31, 2012
New 4.0% Notes [Member]
Debt Instrument [Line Items]
Principal amount	$ 105,322,000	[1]		$ 105,322,000	[1]
Unamortized debt discount and financing costs	(3,700,000)
Net carrying amount of debt component	101,600,000		100,900,000
Carrying amount of equity component	8,900,000
New 4.25% Notes [Member]
Debt Instrument [Line Items]
Principal amount	97,000,000	[1]		97,000,000	[1]
Unamortized debt discount and financing costs	(4,300,000)
Net carrying amount of debt component	92,700,000		92,100,000
Carrying amount of equity component	$ 8,500,000

[1] Dilutive shares associated with the New Convertible Notes are attributable to the premium over the respective conversion prices.