Long-term Debt and Derivatives (Details 4) (USD $)	3 Months Ended	6 Months Ended
Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Interest Rate Swap Contracts
Percentage of debt hedged by interest rate derivatives, excluding revolving credit, as required by credit facility (as a percent)	50.00%		50.00%
Maximum length of time from closing of credit facility to enter into a fixed rate debt arrangement or interest rate swap			100 days
Derivatives instruments impact on consolidated statement of income
Amortization from OCI related to de-designation of derivatives	$ 600,000	$ 4,200,000	$ 2,500,000	$ 8,500,000
Gain (loss) reclassified from OCI in next twelve months	4,600,000		4,600,000
Derivatives Designated as Hedging Instruments
Derivatives instruments impact on consolidated statement of income
Derivatives in a Cash Flow Hedging Relationship, Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	(332,000)	(2,792,000)	(672,000)	(10,178,000)
Derivatives in a Cash Flow Hedging Relationship, Gain (Loss) Reclassified from AOCI into Income (Effective Portion)	(3,625,000)	(6,364,000)	(8,173,000)	(12,859,000)
Derivatives Designated as Hedging Instruments \| Interest rate swap contracts
Derivatives instruments impact on consolidated statement of income
Derivatives in a Cash Flow Hedging Relationship, Gain (Loss) Recognized in OCI on Derivative (Effective Portion)	(332,000)	(2,792,000)	(672,000)	(10,178,000)
Derivatives in a Cash Flow Hedging Relationship, Gain (Loss) Reclassified from AOCI into Income (Effective Portion)	(3,625,000)	(6,364,000)	(8,173,000)	(12,859,000)
Derivatives Not Designated as Hedging Instruments
Derivatives instruments impact on consolidated statement of income
Derivatives Not Designated as Hedging Instruments, Gain (Loss) Recognized in Income on Derivative	(1,000)	(4,000)	(4,000)	(38,000)
Derivatives Not Designated as Hedging Instruments \| Interest rate swap contracts
Derivatives instruments impact on consolidated statement of income
Derivatives Not Designated as Hedging Instruments, Gain (Loss) Recognized in Income on Derivative	$ (1,000)	$ (4,000)	$ (4,000)	$ (38,000)

The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References+ Details

The effective portion of gains and losses (net) on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

+ References+ Details

- Definition

Net of tax effect of the reclassification adjustment for accumulated gains and losses from derivative instrument designated and qualifying as the effective portion of cash flow hedges included in accumulated comprehensive income that was realized in net income during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=6920043&loc=d3e689-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 31, 46
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 130
-Paragraph 18, 19
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 130
-Paragraph 24
-Subparagraph b
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
-Number 51
-Paragraph 38
-Subparagraph c(3)
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5624171-113959

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=6920043&loc=d3e637-108580

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Reclassification Adjustments
-URI http://asc.fasb.org/extlink&oid=6522872

+ Details