CONTINGENT LIABILITIES (Details) claim in Thousands, $ in Millions	1 Months Ended
	Sep. 30, 2010 plaintiff	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jun. 06, 2017 claim
Harrison, et al v. Principal Investments, Inc. et al
Loss Contingencies [Line Items]
Number of claims filed by the company (more than) | claim				16
Harrison, et al v. Principal Investments, Inc. et al | Pending Litigation
Loss Contingencies [Line Items]
Number of plaintiffs | plaintiff	4
Loss contingency accrual		$ 2.3
Reimbursement Offer
Loss Contingencies [Line Items]
Loss contingency accrual			$ 2.0