Net Income per Share (Net Income Per Basic and Diluted Share) (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Numerator
Income used to compute net income per diluted share									$ 110,748	$ 63,606	$ 332,795
Denominator
Total weighted-average shares used to compute net income per basic share (in Shares)									155,394	163,805	163,386
Diluted (in Shares)									156,257	164,192	163,554
Net income per basic share (in Dollars per Share)	$ 0.15	$ 0.14	$ 0.39	$ 0.04	$ (0.06)	$ 0.08	$ 0.03	$ 0.34	$ 0.71	$ 0.39	$ 2.04
Net income per diluted share (in Dollars per Share)	$ 0.15	$ 0.14	$ 0.39	$ 0.04	$ (0.06)	$ 0.08	$ 0.03	$ 0.34	$ 0.71	$ 0.39	$ 2.03
Stock Options [Member]
Debt Instrument [Line Items]
Additional shares included in the calculation of diluted EPS (in Shares)									0	0	16
Restricted Stock [Member]
Debt Instrument [Line Items]
Additional shares included in the calculation of diluted EPS (in Shares)									863	387	152