Net Income per Share (Net Income Per Basic and Diluted Share) (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Earnings Per Share [Abstract]
Net income	$ 93,742	$ 73,502	$ 147,213	$ 113,686
Add back interest expense for convertible notes, net of estimated tax of approximately $3 for each of the three months ended June 30, 2013 and 2012, and $7 and $18 for the six months ended June 30, 2013 and 2012, respectively (see Note 9)	6	6	13	33
Income used to compute net income per diluted share	$ 93,748	$ 73,508	$ 147,226	$ 113,719
Total weighted-average shares used to compute net income per basic share (in Shares)	139,825	139,683	139,821	139,681
Diluted (in Shares)	152,224	142,213	152,784	142,890
Net income per basic share (in Dollars per Share)	$ 0.67	$ 0.53	$ 1.05	$ 0.81
Net income per diluted share (in Dollars per Share)	$ 0.62	$ 0.52	$ 0.96	$ 0.80
Series 2012 Notes [Member]
Debt Instrument [Line Items]
Assumed conversion of debt notes (in Shares)	8,304	2,252	8,693	2,189
May 2015 Notes [Member]
Debt Instrument [Line Items]
Assumed conversion of debt notes (in Shares)	3,825	0	4,004	0
February 2015 Notes [Member]
Debt Instrument [Line Items]
Assumed conversion of debt notes (in Shares)	176	163	176	921
Stock Options [Member]
Debt Instrument [Line Items]
Additional shares included in the calculation of diluted EPS (in Shares)	19	15	19	15
Restricted Stock [Member]
Debt Instrument [Line Items]
Additional shares included in the calculation of diluted EPS (in Shares)	75	100	71	84