Long-Term Debt (Senior Notes Due 2022) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended			0 Months Ended	12 Months Ended		0 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Jul. 17, 2012 Three Point Six Zero Percentage Senior Notes Due Twenty Twenty Two [Member]	Dec. 31, 2012 Three Point Six Zero Percentage Senior Notes Due Twenty Twenty Two [Member]	Sep. 30, 2012 Three Point Six Zero Percentage Senior Notes Due Twenty Twenty Two [Member]	Jul. 30, 2012 6 5/8% Senior Notes Due 2016	Sep. 30, 2012 6 5/8% Senior Notes Due 2016	Dec. 31, 2012 6 5/8% Senior Notes Due 2016	Dec. 31, 2011 6 5/8% Senior Notes Due 2016	Jan. 13, 2006 6 5/8% Senior Notes Due 2016	Jul. 17, 2012 Prior to April Fifteenth Twenty Twenty Two Three Point Six Zero Percentage Senior Notes Due Twenty Twenty Two [Member]	Jul. 17, 2012 On or After April Fifteenth Twenty Twenty Two Three Point Six Zero Percentage Senior Notes Due Twenty Twenty Two [Member]
Debt Instrument [Line Items]
Senior notes, principal amount issued				$ 250,000
Stated interest rate	6.50%			3.60%	3.60%				6.625%	6.625%	6.625%
Maturity				2022	2022				2016
Senior notes, principal amount redeemed							250,000
Senior notes, redemption price as percentage of principal amount							102.208%					100.00%	100.00%
Non-operating expense related to debt retirement	(7,082)	0	0					(7,082)
Pre-payment premium								5,520
Write-off of debt issuance costs	1,277	0	0					1,277
Senior notes, original discount issue				1,183
Senior notes, repurchase price as percentage of principal amount upon change of control and below investment grade rating event				101.00%
Senior notes, maximum number of days from change of control for below investment grade rating event				60 days
Senior notes, minimum debt amount guaranteed by subsidiaries					$ 5,000	$ 5,000