Marketable Securities - Maturities of Held to Maturity Investments (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014
Marketable Securities [Abstract]
Held-to-maturity investments, maturities due within one year	$ 41,143
Held-to-maturity investments, maturities due in one to five years	65,969
Held-to-maturity investments, total maturities due	$ 107,112

Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant