Net Income per Share (Net Income Per Basic and Diluted Share) (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Net Income per Share [Abstract]
Net income	$ 49,408	$ 48,575	$ 73,502	$ 40,184	$ 38,942	$ 45,916	$ 69,986	$ 44,545	$ 211,669	$ 199,389	$ 91,874
Add back interest expense for convertible notes, net of estimated tax of $25,000, $3.0 million, $2.7 million for the years ended December 31, 2012, 2011 and 2010, respectively (see Note 12)									46	5,544	5,087
Income used to compute net income per diluted share									$ 211,715	$ 204,933	$ 96,961
Total weighted-average shares used to compute net income per basic share (in Shares)									139,711	139,663	126,578
Shares used to compute net income per diluted share (in Shares)									146,403	177,441	178,801
Net income per basic share (in Dollars per Share)	$ 0.35	$ 0.35	$ 0.53	$ 0.29	$ 0.28	$ 0.33	$ 0.50	$ 0.32	$ 1.52	$ 1.43	$ 0.73
Net income per diluted share (in Dollars per Share)	$ 0.34	$ 0.32	$ 0.52	$ 0.29	$ 0.24	$ 0.28	$ 0.38	$ 0.25	$ 1.45	$ 1.15	$ 0.54
Series 2012 Notes [Member]
Debt Instrument [Line Items]
Assumed conversion of debt notes (in Shares)									4,944	0	0
2012 Notes [Member]
Debt Instrument [Line Items]
Assumed conversion of debt notes (in Shares)									0	9,790	29,870
February 2015 Notes [Member]
Debt Instrument [Line Items]
Assumed conversion of debt notes (in Shares)									631	27,950	4,229
Due May 2015 [Member]
Debt Instrument [Line Items]
Assumed conversion of debt notes (in Shares)									1,005	0	0
2023 Notes [Member]
Debt Instrument [Line Items]
Assumed conversion of debt notes (in Shares)									0	0	18,012
Restricted Stock [Member]
Debt Instrument [Line Items]
Incremental common shares attributable to share based payment arrangements (in Shares)									17	25	103