CONTRIBUTING EMPLOYEE OWNERSHIP PLAN (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Defined Contribution Plan Disclosure [Line Items]
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 8.6	$ 8.7
Employer matching contributions to employee ownership plan	$ 3.7	$ 2.9
Minimum
Defined Contribution Plan Disclosure [Line Items]
Contribution To Individual Retirement Account Percentage Of Employees Eligible Compensation	5.00%
Maximum
Defined Contribution Plan Disclosure [Line Items]
Contribution To Individual Retirement Account Percentage Of Employees Eligible Compensation	7.50%