SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of New Accounting Pronouncement Impact (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Summary Of Significant Accounting Policies [Line Items]
Deferred revenues	$ 4,861,000				$ 5,746,000				$ 4,861,000	$ 5,746,000
Total Revenue Change	70,035,000	$ 68,907,000	$ 69,642,000	$ 72,133,000	$ 74,117,000	$ 73,940,000	$ 74,315,000	$ 75,924,000	280,718,000	298,297,000	$ 318,293,000
Total Expense Reduction									275,944,000	$ 391,367,000	$ 344,188,000
Difference Between Revenue Guidance In Effect Before And After Topic 606 | Accounting Standards Update 2014-09 | Pro Forma
Summary Of Significant Accounting Policies [Line Items]
Commissions	23,600								23,600
Deferred revenues	5,400								5,400
Deferred costs	$ (6,300)								(6,300)
Total Revenue Change									0.70
Total Expense Reduction									$ (2,100)