CHANGE IN ACCOUNTING POLICIES AND ATS ACQUISITION - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Jan. 01, 2018	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract liability		$ 138,165		$ 138,165		$ 117,679
Other operating expenses		575,749	$ 591,222	1,158,772	$ 1,199,366
Contract asset		24,358		24,358		24,329
Goodwill		$ 8,004,808		$ 8,004,808		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			(5,979)		(9,396)
Contract asset						24,329
Goodwill						0
ATS Acquisition | Restatement Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other operating expenses			$ 8,566		$ 8,566
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