Investments - Schedule of Investments (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013
Schedule of Available-for-sale Securities [Line Items]
Cost	$ 147,728
Gross Unrealized Gains	54
Gross Unrealized Losses	1,731
Fair Value	146,051
U.S. treasury securities
Schedule of Available-for-sale Securities [Line Items]
Cost	124,919
Gross Unrealized Gains	54
Gross Unrealized Losses	0
Fair Value	124,973
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Cost	22,809
Gross Unrealized Gains	0
Gross Unrealized Losses	1,731
Fair Value	$ 21,078

Amount of debt securities categorized neither as held-to-maturity nor trading.

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+ Details

- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

+ References+ Details