Share Based Compensation - Stock Option Activity under Stock Option Plans (Detail) (USD $)	12 Months Ended
Dec. 31, 2012	Dec. 31, 2010
Number of Shares
Beginning balance (in shares)	1,035,871
Granted (in shares)	46,801
Exercised (in shares)	(10,500)
Cancelled (in shares)	(165,536)
Ending balance (in shares)	906,636
Vested and Expected to Vest at December 31, 2012 (in shares)	906,636
Exercisable at December 31, 2012 (in shares)	838,586
Weighted-Average Exercise Price
Beginning balance (usd per share)	$ 22.57	$ 23.01
Granted (usd per share)	$ 11.69
Exercised (usd per share)	$ 7.39
Cancelled (usd per share)	$ 25.87
Ending balance (usd per share)	$ 21.58	$ 23.01
Vested and Expected to Vest at December 31, 2012 (usd per share)	$ 21.58
Exercisable at December 31, 2012 (usd per share)	$ 22.61
Weighted Average Remaining Contractual Term
Outstanding December 31, 2012	4 years 0 months 29 days
Vested and Expected to Vest at December 31, 2012	4 years 0 months 29 days
Exercisable at December 31, 2012	3 years 7 months 17 days
Aggregate Intrinsic Value
Outstanding December 31, 2012	$ 1,046,301
Vested and Expected to Vest at December 31, 2012	1,046,301
Exercisable at December 31, 2012	$ 721,758

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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Weighted average remaining contractual term for vested portions of options outstanding and currently exercisable or convertible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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