EMPLOYEE BENEFIT PLANS - Restricted Stock Units (Details) - Restricted Stock Units $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($) quarter $ / shares shares	Mar. 31, 2019 quarter shares
Restricted Stock Units
Unvested at the beginning of the period (in shares)	1,463,499
Granted (in shares)	1,423,953	1,128,005
Vested (in shares)	(394,281)
Forfeited (in shares)	(14,587)
Unvested at the end of the period (in shares)	2,478,584
Weighted Average Grant Date Fair Value Per Unit
Unvested at the beginning of the period (in dollars per share) | $ / shares	$ 25.08
Granted (in dollars per share) | $ / shares	29.05
Vested (in dollars per share) | $ / shares	25.28
Forfeited (in dollars per share) | $ / shares	24.80
Unvested at the end of the period (in dollars per share) | $ / shares	$ 27.33
Award vesting percentage	33.33%
Unrecognized compensation costs | $	$ 48
Vesting period	3 years
Period for recognition of unrecognized compensation costs	2 years 3 months 18 days
Time based vesting, three year period from grant date
Restricted Stock Units
Granted (in shares)	493,929	243,506
Weighted Average Grant Date Fair Value Per Unit
Vesting date of grant anniversary subject to specific conditions	3 years	3 years
Time based vesting, four year period from grant date
Restricted Stock Units
Granted (in shares)	104,167
Weighted Average Grant Date Fair Value Per Unit
Vesting date of grant anniversary subject to specific conditions	4 years
Third anniversary vesting date
Weighted Average Grant Date Fair Value Per Unit
Number of restricted stock units vested on third anniversary of grant date (in shares)		318,327
Vesting period	3 years	3 years
Eleven quarter vesting period
Restricted Stock Units
Granted (in shares)	359,713
Weighted Average Grant Date Fair Value Per Unit
Vesting period, quarterly periods | quarter	11
Performance based vesting on the third anniversary
Restricted Stock Units
Granted (in shares)	386,016
Performance based vesting over a four year period | Officer
Restricted Stock Units
Granted (in shares)	80,128
Performance based vesting
Weighted Average Grant Date Fair Value Per Unit
Award vesting performance period	3 years
Performance based vesting | Minimum
Weighted Average Grant Date Fair Value Per Unit
Award vesting percentage	0.00%
Performance based vesting | Maximum
Weighted Average Grant Date Fair Value Per Unit
Award vesting percentage	200.00%
Nine quarter vesting period
Restricted Stock Units
Granted (in shares)		566,172
Weighted Average Grant Date Fair Value Per Unit
Vesting period, quarterly periods | quarter		9