Financial Instruments Available-for-sale Securities (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 239,113
Gross Unrealized Gains	434
Gross Unrealized Losses	(159)
Fair Value	239,388	0
Proceeds from sales and maturities of securities	7,770
Gross realized gains	20
Gross realized losses	(39)
Net unrealized gains	176
Income tax expense on net unrealized gains	99
Corporate Bond Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	108,300
Gross Unrealized Gains	340
Gross Unrealized Losses	(69)
Fair Value	108,571
US Treasury and Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	106,335
Gross Unrealized Gains	60
Gross Unrealized Losses	(79)
Fair Value	106,316
Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost	24,478
Gross Unrealized Gains	34
Gross Unrealized Losses	(11)
Fair Value	$ 24,501
Minimum [Member] \| Corporate Bond Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment maturity period	1 month
Minimum [Member] \| US Government Agencies Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment maturity period	3 months
Minimum [Member] \| Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment maturity period	2 years
Minimum [Member] \| Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment maturity period	4 years
Maximum [Member] \| Corporate Bond Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment maturity period	5 years
Maximum [Member] \| US Government Agencies Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment maturity period	3 years
Maximum [Member] \| Asset-backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment maturity period	7 years
Maximum [Member] \| Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Investment maturity period	29 years

Accumulated appreciation or loss, net of tax, in value of the total of available-for-sale securities at the end of an accounting period.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 14A

-URI http://asc.fasb.org/extlink&oid=28358780&loc=SL7669686-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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Amount of investment in debt and equity securities categorized neither as trading securities nor held-to-maturity securities and intended be sold or mature one year or operating cycle, if longer.

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This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

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This item represents the gross loss realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.

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The cash inflow associated with the sale of debt and equity securities classified as available-for-sale securities.

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Tax related to the accumulated appreciation or loss in value of the total of available-for-sale securities at the end of an accounting period.

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Amount of accumulated pre-tax unrealized gains before deducting pre-tax unrealized loss on investments in available-for-sale securities impacting investments.

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No definition available.

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Amount of accumulated pre-tax unrealized loss before deducting pre-tax unrealized gain on investments in available-for-sale debt securities impacting investments.

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Investment Maturity, Term

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