NET INCOME PER SHARE - Computation of Basic and Diluted Net Income Per Share (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Earnings Per Share, Basic and Diluted [Abstract]
Net income	$ 104.0	$ 159.1	$ 148.3	$ 348.0
Weighted-average shares outstanding used in basic calculation	36.9	39.9	37.6	40.1
Add: Dilutive effect of potential common shares	0.7	0.9	0.7	1.0
Weighted-average shares used in computing diluted net income per share	37.6	40.8	38.3	41.1
Net income per share:
Basic (in dollars per share)	$ 2.82	$ 3.99	$ 3.94	$ 8.68
Diluted (in dollars per share)	$ 2.77	$ 3.90	$ 3.87	$ 8.47