CHANGE IN ACCOUNTING POLICIES AND ATS ACQUISITION - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Jan. 01, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract liability		$ 173,956		$ 173,956		$ 117,679
Other operating expenses		569,070	$ 570,111	1,727,842	$ 1,769,477
Contract asset		25,806		25,806		24,329
Goodwill		$ 8,012,416		$ 8,012,416		8,019,861
Impact of ASC 606 | Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract liability						6,978
Other operating expenses			(4,094)		(13,490)
Contract asset						24,329
Goodwill						0
ATS Acquisition | Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other operating expenses			$ 16,629		$ 25,195
Goodwill						$ 23,101
Installation Services | Impact of ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect on retained earnings, net of tax	$ 5,093
Cumulative effect on retained earnings, tax	1,885
Commissions | Impact of ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect on retained earnings, net of tax	17,759
Cumulative effect on retained earnings, tax	$ 6,570