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Senior Unsecured Notes (Narrative) (Details) (USD $)
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12 Months Ended | ||||
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Dec. 31, 2013
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Dec. 31, 2012
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| Debt Instrument [Line Items] | |||||
| Proceeds from the sale of senior unsecured notes | $ 268,928,000 | $ 547,926,000 | |||
| Repayments of senior unsecured notes | 100,000,000 | 221,019,000 | |||
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3.150% Senior Unsecured Note, Due May 15, 2023 [Member]
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| Debt Instrument [Line Items] | |||||
| Face amount of senior unsecured notes | 275,000,000 | ||||
| Interest rate of senior unsecured notes | 3.15% | ||||
| Maturity date of the senior unsecured notes | May 15, 2023 | ||||
| Proceeds from the sale of senior unsecured notes | 266,500,000 | ||||
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4.600% Senior Unsecured Notes, Due June 15, 2013 [Member]
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| Debt Instrument [Line Items] | |||||
| Interest rate of senior unsecured notes | 4.60% | [1] | |||
| Maturity date of the senior unsecured notes | Jun. 15, 2013 | [1] | |||
| Repayments of senior unsecured notes | $ 100,000,000 | ||||
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| X | ||||||||||
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- Definition
Face (par) amount of debt instrument at time of issuance. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition
Contractual interest rate for funds borrowed, under the debt agreement. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Details
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- Definition
Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The cash inflow from the issuance of long-term debt that is not secured by collateral. Excludes proceeds from tax exempt unsecured debt. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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| X | ||||||||||
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- Definition
The cash outflow to repay long-term debt that is not secured by collateral. Excludes repayments of tax exempt unsecured debt. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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