|
Stock incentive plans (Details)
|
12 Months Ended | ||||||||
|---|---|---|---|---|---|---|---|---|---|
|
Dec. 31, 2012
|
Dec. 31, 2011
|
Dec. 31, 2010
|
Dec. 31, 2009
|
Dec. 31, 2012
2011 Plan
|
Dec. 31, 2011
2011 Plan
|
Mar. 31, 2011
2011 Plan
|
Dec. 31, 2012
2001 Plan
|
Dec. 31, 2011
2001 Plan
|
|
| Stock incentive plan | |||||||||
| Common stock shares reserved for issuance | 5,511,288 | ||||||||
| Annual percentage increase alternative, increase in common stock reserved for issuance as a percentage of common stock outstanding | 4.50% | ||||||||
| Annual fixed increase alternative, increase in shares of common stock reserved for issuance (in shares) | 3,000,000 | ||||||||
| Outstanding stock options (in shares) | 5,045,000 | 6,601,000 | 5,288,000 | 5,281,000 | 2,700,000 | 2,261,000 | 2,345,000 | 4,340,000 | |
| Shares of common stock granted under the plan | 3,670,481 |