QUARTERLY FINANCIAL INFORMATION (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Quarterly results:
Total revenue	$ 613,748	$ 675,594	$ 676,276	$ 664,691	$ 565,023	$ 621,607	$ 619,081	$ 624,272	$ 2,630,308	$ 2,429,983	$ 2,072,179
Gross profit	227,152	253,945	255,892	256,137	214,377	235,214	239,437	240,709	993,127	929,738	753,833
Operating income	86,334	125,974	123,671	124,520	87,533	111,177	117,060	112,069	460,498	427,840	282,507
Net income	$ 47,657	$ 73,033	$ 71,688	$ 72,643	$ 47,438	$ 62,229	$ 66,671	$ 63,857	$ 265,021	$ 240,196	$ 132,333
Weighted average shares outstanding:
Basic (in shares)	94,636	95,183	97,428	98,997	99,205	102,541	106,517	105,805	96,481	103,503	100,261
Diluted (in shares)	95,477	96,078	98,333	99,861	100,119	103,721	107,927	107,746	97,383	104,911	103,010
Earnings per share:
Basic (in dollars per share)	$ 0.50	$ 0.77	$ 0.74	$ 0.73	$ 0.48	$ 0.61	$ 0.63	$ 0.60	$ 2.75	$ 2.32	$ 1.27
Diluted (in dollars per share)	$ 0.50	$ 0.76	$ 0.73	$ 0.73	$ 0.47	$ 0.60	$ 0.62	$ 0.59	$ 2.72	$ 2.29	$ 1.24