SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Redeemable Noncontrolling Interests (Details) |
6 Months Ended |
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Jun. 30, 2017 | |
Accounting Policies [Abstract] | |
Expiration period of redeemable noncontrolling interests, low end of range | 1 year |
Expiration period of redeemable noncontrolling interests, high end of range | 3 years |