Earnings Per Share (Schedule Of Convertible Note Premium Share Information) (Detail) (Unsecured Debt [Member], Convertible Debt [Member], USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
2011 4.0% Notes [Member]
Earnings Per Share [Line Items]
Number of conversion shares, principal amount	6,683	6,683	6,683	6,683
Weighted average equivalent premium shares	3,476	794	3,240	631
2011 4.25% Notes [Member]
Earnings Per Share [Line Items]
Number of conversion shares, principal amount	6,268	6,268	6,268	6,268
Weighted average equivalent premium shares	3,314	845	3,097	694
Weighted Average [Member] | 2011 4.0% Notes [Member]
Earnings Per Share [Line Items]
Weighted average actual per share price	$ 32.84	$ 17.89	$ 30.59	$ 17.40
Weighted average premium value	$ 114,176	$ 14,208	$ 99,104	$ 10,975
Weighted Average [Member] | 2011 4.25% Notes [Member]
Earnings Per Share [Line Items]
Weighted average actual per share price	$ 32.84	$ 17.89	$ 30.59	$ 17.40
Weighted average premium value	$ 108,864	$ 15,106	$ 94,728	$ 12,073