BENEFIT PLANS: (Details) $ in Millions	6 Months Ended
	Jun. 30, 2015 USD ($) plan	Jun. 30, 2014 USD ($)
BENEFIT PLANS:
Number of expatriate noncontributory defined benefit pension plans | plan	2
Post retirement defined benefit plan
Defined benefit plan, net periodic benefit cost
Service cost	$ 0.5	$ 0.6
Interest cost	0.5	0.7
Expected return on plan assets	(1.6)	(1.8)
Amortization of transition obligation	(0.2)	(0.2)
Amortization of net loss/(gain)	0.2
Net periodic benefit costs	(0.6)	(0.7)
Post retirement defined benefit plan | Maximum
Defined benefit plan, net periodic benefit cost
Amortization of net loss/(gain)		(0.1)
Post-retirement Health Care Plan
Defined benefit plan, net periodic benefit cost
Interest cost	0.6	0.7
Amortization of net loss/(gain)	(0.1)	(0.2)
Net periodic benefit costs	0.5	0.5
Post-retirement Health Care Plan | Maximum
Defined benefit plan, net periodic benefit cost
Amortization of prior service cost (credit)	$ 0.1	$ 0.1