Accumulated Other Comprehensive Income (Loss) Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Accumulated Other Comprenhensive Income (Loss) [Roll Forward]
Derivative instruments, beginning balance	$ 2,244	$ (4,729)	$ 2,921	$ 1,186
Derivative instruments, before tax	10,895	(11,951)	2,711
Derivative instruments, tax effect	(3,922)	4,301	(976)
Derivative instruments, ending balance	2,244	(4,729)	2,921	1,186
Pension, Postretirement and Other Post-Employment Benefits, beginning balance	(18,286)	(4,676)	(10,679)	(20,539)
Pension, Postretirement and Other Post-Employment Benefits, before tax	(21,265)	9,345	15,406
Pension, Postretirement and Other Post-Employment Benefits, tax effect	7,655	(3,342)	(5,546)
Pension, Postretirement and Other Post-Employment Benefits, beginning balance	(18,286)	(4,676)	(10,679)	(20,539)
Available-for-Sale Securities, beginning balance	(465)	1,455	1,341	(500)
Available-for-sale Securities, before tax	(3,000)	176	2,877
Available-for-sale Securities, tax effect	1,080	(62)	(1,036)
Accumulated Other Comprehensive Income (Loss), beginning balance	(16,507)	(7,950)	(6,417)	(19,853)
Accumulated Other Comprehensive Income (Loss), before tax	(13,370)	(2,430)	20,994
Accumulated Other Comprehensive Income (Loss), tax effect	4,813	897	(7,558)
Accumulated Other Comprehensive Income (Loss), ending balance	$ (16,507)	$ (7,950)	$ (6,417)	$ (19,853)