Fair Value of Financial Instruments (Cash and Cash Equivalents, Available-for-sale Securities, Restricted Cash Reconciliation) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized cost, total	$ 166,656	$ 132,766
Unrealized Gains	37	45
Unrealized Losses	(27)	(7)
Fair value	166,666	132,804
Cash and Cash Equivalents
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized cost, total	76,504	42,368
Unrealized Gains	0	1
Unrealized Losses	0	0
Fair value	76,504	42,369
Short-term Investments
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized cost, total	50,716	54,810
Unrealized Gains	10	17
Unrealized Losses	(12)	0
Fair value	50,714	54,827
Long-Term Investments
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized cost, total	39,436	35,588
Unrealized Gains	27	27
Unrealized Losses	(15)	(7)
Fair value	39,448	35,608
Cash \| Cash and Cash Equivalents
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized cost, total	36,024	27,488
Fair value	36,024	27,488
Money market funds \| Cash and Cash Equivalents
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized cost, total	39,180	183
Unrealized Gains	0	0
Unrealized Losses	0	0
Fair value	39,180	183
U.S. government agencies \| Cash and Cash Equivalents
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized cost, total	300
Unrealized Gains	0
Unrealized Losses	0
Fair value	300
U.S. government agencies \| Short-term Investments
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized cost, total	33,280	4,004
Unrealized Gains	3	0
Unrealized Losses	(6)	0
Fair value	33,277	4,004
U.S. government agencies \| Long-Term Investments
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized cost, total	3,101	15,256
Unrealized Gains	0	22
Unrealized Losses	(2)	(4)
Fair value	3,099	15,274
Commercial paper \| Cash and Cash Equivalents
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized cost, total	1,000	14,697
Unrealized Gains	0	1
Unrealized Losses	0	0
Fair value	1,000	14,698
Commercial paper \| Short-term Investments
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized cost, total	4,998	32,784
Unrealized Gains	1	6
Unrealized Losses	0	0
Fair value	4,999	32,790
Corporate bonds \| Short-term Investments
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized cost, total	12,438	16,894
Unrealized Gains	6	11
Unrealized Losses	(6)	0
Fair value	12,438	16,905
Corporate bonds \| Long-Term Investments
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized cost, total	20,243	14,835
Unrealized Gains	22	1
Unrealized Losses	(10)	(3)
Fair value	20,255	14,833
Municipal bonds \| Short-term Investments
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized cost, total		1,128
Unrealized Gains		0
Unrealized Losses		0
Fair value		1,128
Asset-backed securities \| Long-Term Investments
Financial Instruments, Financial Assets, Balance Sheet Groupings [Abstract]
Amortized cost, total	16,092	5,497
Unrealized Gains	5	4
Unrealized Losses	(3)	0
Fair value	$ 16,094	$ 5,501

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

No definition available.

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- Definition

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

No definition available.

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- Definition

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.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.2)

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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.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=28360136&loc=d3e22054-111558

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

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