INCOME TAXES - EFFECTIVE INCOME TAX RECONCILIATION (DETAILS) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Tax Disclosure [Abstract]
U.S. federal tax rate	35.00%	35.00%	35.00%
Income before income tax	$ 514	$ 394	$ 406
Expected tax expense	180	138	142
Nondeductible expenses	3	1	2
State income taxes	14	10	11
Other—net	1	0	0
Total tax expense related to income	$ 198	$ 149	$ 155
Effective tax rate	38.50%	37.90%	38.10%