NATURE OF OPERATIONS AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Recent Accounting Pronouncements (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Aug. 31, 2016	Dec. 31, 2018	Dec. 31, 2017		Dec. 31, 2016		Jan. 01, 2019	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of adoption of new accounting standard			$ 2,100					$ 2,264
Net cash flows from operating activities		$ 647,418	431,413	[1]	$ 611,590	[1]
Net cash flow from (used in) investing activities		(118,211)	114,584	[1]	(609,528)	[1]
Net cash flow from financing activities		$ (464,817)	189,759	[1]	104,425	[1]
Accounting Standards Update 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of adoption of new accounting standard			2,100
As Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash flows from operating activities			431,104		591,766
Net cash flow from (used in) investing activities			(198,025)		(606,003)
Net cash flow from financing activities			188,263		124,249
Adjustment (a) | Accounting Standards Update 2016-15
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash flows from operating activities			309		19,824
Net cash flow from (used in) investing activities			312,609		(3,525)
Net cash flow from financing activities			$ 1,496		$ (19,824)
6.375% Senior Unsecured Notes due 2021 | Senior Notes
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Prepayment penalty	$ 19,800
Interest rate (as a percent)	637.50%
Subsequent Event | Scenario, Forecast | Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Percent increase in right-of-use lease assets (less than)							5.00%
Percent increase in lease liabilities (less than)							5.00%

[1] See Recent Accounting Pronouncements within Note 1. Nature of Operations and Summary of Significant Accounting Policies for a discussion of the adoption of new accounting principles related to the classification of certain cash receipts and cash payments.