Stock-based Compensation - Shares Available for Future Grants and Reserve for Issuance (Parenthetical) (Details) - shares	Dec. 31, 2015	Dec. 31, 2014
Director
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Directors deferred compensation account (in shares)	142,913	135,722

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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