FINANCIAL INSTRUMENTS (Tables)

12 Months Ended

Dec. 31, 2013

Fair Value Disclosures [Abstract]

Assets and liabilities measured at fair value on recurring basis

Certain of our assets and liabilities are required to be measured at fair value on a recurring basis. Assets and liabilities measured at fair value are summarized below (in thousands):

			Estimated fair value measurements
	Carrying value		Quoted prices in active markets (Level 1)		Significant other observable inputs (Level 2)		Significant other unobservable inputs (Level 3)
December 31, 2013:
Assets - cash equivalents	$	1,063,500	$	1,063,500	$	—	$	—
December 31, 2012:
Assets - cash equivalents	$	987,420	$	987,420	$	—	$	—

Fair value of financial instruments

Estimated fair values and related carrying values of our long-term debt securities at December 31 are presented below (in thousands):

	2013				2012
	Fair value		Carrying value		Fair value		Carrying value
5% Senior Notes, due 2017	$	433,879	$	398,961	$	445,568	$	398,678
7.875% Senior Notes, due 2019	603,177		498,171		617,076		497,842
4.875% Senior Notes, due 2022	711,816		713,208		761,509		714,775
5.4% Senior Notes, due 2042	368,602		398,360		406,493		398,303
	$	2,117,474	$	2,008,700	$	2,230,646	$	2,009,598