SHARE INCENTIVE PLANS: (Stock option rollforward) (Details) - Employee stock option [Member] - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Feb. 23, 2016	Dec. 31, 2015
Number of Shares
Options outstanding at the beginning of the period (in shares)	2,028,595
Options exercised (in shares)	(198,808)
Options canceled (in shares)	(30,982)
Options outstanding at the end of the period (in shares)	1,798,805
Weighted Average Exercise Price
Weighted-average exercise price, options outstanding at the beginning of the period (in USD per share)	$ 30.81
Weighted-average exercise price, options exercised (in USD per share)	15.83
Weighted-average exercise price, options canceled (in USD per share)	83.46
Weighted-average exercise price, options outstanding at the end of the period (in USD per share)	$ 31.55
Pretax intrinsic value of options exercised	$ 6.5	$ 8.6
Share price (in USD per share)	$ 47.96		$ 46.40
Pretax intrinsic value of options outstanding	$ 42.9			$ 40.2
Pretax intrinsic value of exercisable options	$ 42.7			$ 39.9