Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Treasury stock, shares	132,142us-gaap_TreasuryStockShares	104,247us-gaap_TreasuryStockShares
Voting Common Stock
Common stock, par value (in dollars per share)	0.0001	0.0001
Common stock, shares authorized	240,000,000	240,000,000
Common stock, shares issued	72,907,827	72,774,920
Common stock, shares outstanding	72,775,685	72,670,673
Non-Voting Common Stock
Common stock, par value (in dollars per share)	0.0001	0.0001
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	0	0
Common stock, shares outstanding	0	0

Face amount or stated value per share of common stock.

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

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

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

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Number of common and preferred shares that were previously issued and that were repurchased by the issuing entity and held in treasury on the financial statement date. This stock has no voting rights and receives no dividends.

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