Amount of noncash expense included in interest expense to issue debt and obtain financing associated with the related debt instruments. Alternate captions include noncash interest expense.

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

-Publisher FASB

-Name Accounting Standards Codification

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-Number 210

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- Definition

Amount of the cost of borrowed funds accounted for as interest expense for debt.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

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Represents the portion of interest incurred in the period on debt arrangements that was charged against earnings, excluding amortization of debt discount (premium) and financing costs.

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Long-term Debt (Interest Expense of Long-term Debt) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Total interest expense	$ 25,518us-gaap_InterestExpenseDebt	$ 5,572us-gaap_InterestExpenseDebt	$ 0us-gaap_InterestExpenseDebt
Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Amortization of debt issuance costs	3,373	743
Total interest expense	24,010	5,551
Unsecured Senior Notes [Member] \| Interest expense at an annual rate of 2.50% [Member]
Debt Instrument [Line Items]
Interest expense	15,981	4,808
Unsecured Senior Notes [Member] \| Interest expense at an annual rate of 0.50% [Member]
Debt Instrument [Line Items]
Interest expense	1,042
Unsecured Senior Notes [Member] \| Interest expense at an annual rate of 1.75% [Member]
Debt Instrument [Line Items]
Interest expense	$ 3,614