NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Share Repurchase Program (Details) - USD ($) shares in Millions		1 Months Ended
	Aug. 09, 2017	Sep. 30, 2016	Aug. 31, 2017	Mar. 20, 2014
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount				$ 150,000,000.0
Stock repurchase program, additional authorized repurchase amount		$ 150,000,000
Subsequent Event | Class A Common Stock
Equity, Class of Treasury Stock [Line Items]
Treasury stock, shares acquired (in shares)	0.2
Treasury stock, value acquired	$ 7,800,000
Stock repurchase program, remaining authorized repurchase amount			$ 111,400,000