Fair Value Measurements (Table)

3 Months Ended

Mar. 31, 2012

Fair Value Disclosures [Abstract]

Fair value measurements

		Level within	March 31,				December 31,
		the Fair Value	2012				2011
		Hierarchy	Book Value			Fair Value	Book Value		Fair Value
(Dollars in thousands)
Cash and cash equivalents		1	$	511,078	$	511,078	$	424,155	$	424,155
Short-term investments (1)(2)
	Certificates of deposit	1		—		—		—		—
	Government-backed securities (3)	1		116,368		116,368		127,039		127,039
Long-term investments (1)(4)
	Government-backed securities (3)	1		40,276		40,324		30,057		30,140
Long-term debt (5)
	6.95% Senior Notes	1		342,000		356,774		342,000		364,162
	6.7% Senior Notes	2		534,225		526,535		534,111		534,860

• Designated as held-to-maturity investments and recorded at amortized cost in the Consolidated Balance Sheet.
• Maturities are less than twelve months from the respective balance sheet dates.
• Includes U.S. treasuries and corporate notes guaranteed under the Federal Deposit Insurance Corporation's Temporary Liquidity Guarantee Program.
• At March 31, 2012, maturities range between 15 and 24 months.
• Excludes capital lease obligations and current portion of Long-term debt.