CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Dec. 31, 2012	Dec. 31, 2011	Mar. 31, 2013	Mar. 31, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2010
Statement of Other Comprehensive Income [Abstract]
Net loss	$ (2,978)	$ (1,306)	$ (7,157)	$ 2,979	$ (10,272)	$ (5,211)	$ (3,813)	$ (7,280)	$ (4,178)	$ (11,093)	$ (5,484)	$ (16,304)	$ (8,462)	$ (26,576)	$ (52,033)	$ (25,359)
Other comprehensive income (loss), net of tax:
Deferred loss on derivatives designated as cash flow hedges													(7,921)	0	0
Change in the funded status status of retiree benefit obligations		0	0	0	26,700		0	0	0	0	0		10,969	(26,574)	36,731	(5,938)
Income tax expense		0	0	0	0	0	0	0	0	0	0	0	(1,066)	0	(14,053)	0
Total comprehensive income (loss), net of tax		$ (1,306)	$ (7,157)	$ 2,979	$ (36,972)	$ (5,211)	$ (3,813)	$ (7,280)	$ (4,178)	$ (11,093)	$ (5,484)	$ (16,304)	$ (6,480)	$ (53,150)	$ (29,355)	$ (31,297)