Additional Cash Flow Information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash paid during the year for:
Interest	$ 7,421us-gaap_InterestPaid	$ 10,568us-gaap_InterestPaid	$ 5,633us-gaap_InterestPaid
Income taxes	88,277us-gaap_IncomeTaxesPaid	104,324us-gaap_IncomeTaxesPaid	62,824us-gaap_IncomeTaxesPaid
Non-cash financing activities:
Assets acquired under capital lease obligations	$ 93us-gaap_CapitalLeaseObligationsIncurred	$ 414us-gaap_CapitalLeaseObligationsIncurred	$ 1,590us-gaap_CapitalLeaseObligationsIncurred

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The increase during the period in capital lease obligations due to entering into new capital leases.

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-Publisher FASB

-Name Accounting Standards Codification

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The amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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The amount of cash paid for interest during the period.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

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