EMPLOYEE BENEFITS - Stock Ownership and Incentive Plans (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Employee Stock Ownership, 401(K) And Deferred Compensation Plan
Annual expenses for incentive plans	$ 19.2	$ 20.4	$ 23.1
ESOP and 401(k) Plans
Employee Stock Ownership, 401(K) And Deferred Compensation Plan
Vesting period of profit sharing contributions	3 years
Expenses recognized	$ 11.7	$ 11.6	$ 14.1
Employee Stock Ownership Plan (ESOP)
Employee Stock Ownership, 401(K) And Deferred Compensation Plan
Shares purchased under defined contribution plan	112,608	178,492	178,987
Average price of shares purchased (in dollars per share)	$ 64.20	$ 49.98	$ 44.43
Aggregate price of shares purchased	$ 7.2	$ 8.9	$ 7.9
Shares held by the ESOP	3,360,325
Employee 401(k) Plans
Employee Stock Ownership, 401(K) And Deferred Compensation Plan
Employer contribution as a percent of eligible compensation	3.00%
Vesting percentage in basic and voluntary contributions	100.00%
Deferred compensation plan
Employee Stock Ownership, 401(K) And Deferred Compensation Plan
Shares purchased under defined contribution plan	6,702	9,348	9,920
Average price of shares purchased (in dollars per share)	$ 61.61	$ 53.15	$ 44.40
Aggregate price of shares purchased	$ 0.4	$ 0.5	$ 0.4
Assets held under trust	$ 39.9