CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME [Abstract]
NET INCOME	$ 180,602	$ 736,841	$ 279,995
Pension and other postretirement benefit adjustments, net of tax:
Prior service credit arising during the period	626	0	0
Net (loss) gain arising during the period, net of tax benefit of $8,340, $43,017 and $2,035, respectively	(15,488)	(79,888)	(3,779)
Amortization of net loss, net of tax expense of $11,986, $7,611 and $6,810, respectively	22,259	14,135	12,648
Amortization of transition obligation, net of tax expense of $166, $297 and $232, respectively	308	552	430
Amortization of prior service credit, net of tax benefit of $1,678, $8,063 and $2,408, respectively	(3,116)	(14,975)	(4,473)
OTHER COMPREHENSIVE INCOME	4,589	(80,176)	4,826
COMPREHENSIVE INCOME	$ 185,191	$ 656,665	$ 284,821