CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Statement of Comprehensive Income [Abstract]
Net income	$ 20,204	$ 45,941	$ 2,932	$ 106,586
Other comprehensive income, net of tax:
Net actuarial pension loss amortization, net of income tax of $182, $259, $393 and $531	286	404	619	827
Prior service (credit) amortization, net of income tax of $151, $152, $302 and $303	(238)	(237)	(476)	(474)
Unrealized gains (losses) on available-for-sale securities, net of income tax of $0, $0, $0 and $0	0	2	0	(21)
Other comprehensive income, net of tax	48	169	143	332
Comprehensive income	$ 20,252	$ 46,110	$ 3,075	$ 106,918