| Component: (Network and Table) | |
|---|---|
| Network | 2412406 - Disclosure - Share-based compensation (Rollforward Of Company's Restricted Stock) (Details) (http://www.acegroup.com/role/ShareBasedCompensationRollforwardOfCompanysRestrictedStockDetails) |
| Table | Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] |
| Reporting Entity [Axis] | 0000896159 (http://www.sec.gov/CIK) |
| Award Type [Axis] | Restricted Stock [Member] |
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | Period [Axis] | ||
|---|---|---|---|
2012-01-01 - 2012-12-31 | 2011-01-01 - 2011-12-31 | 2010-01-01 - 2010-12-31 | |
Number of Restricted Stock [Roll Forward] | |||
Number of unvested restricted stock, beginning of period | 4,851,490 | 5,305,732 | 4,873,429 |
Number of restricted stock, granted | 1,589,178 | 1,808,745 | 2,461,076 |
Number of restricted stock, vested and issued | (1,923,385) | (1,929,189) | (1,771,423) |
Number of restricted stock, forfeited | (262,436) | (333,798) | (257,350) |
Number of unvested restricted stock, end of period | 4,254,847 | 4,851,490 | 5,305,732 |
Weighted-Average Grant-Day Fair Value [Roll Forward] | |||
Weighted average grant-day fair value of unvested restricted stock outstanding, beginning of period (US$ per share) | 52.20 | 48.74 | 48.25 |
Weighted average grant-day fair value of restricted stock, granted (US$ per share) | 73.46 | 60.01 | 51.09 |
Weighted average grant-day fair value of restricted stock, vested and issued (US$ per share) | 52.71 | 50.82 | 50.79 |
Weighted average grant-day fair value of restricted stock, forfeited (US$ per share) | 58.40 | 47.46 | 47.93 |
Weighted average grant-day fair value of unvested restricted stock outstanding, end of period (US$ per share) | 59.53 | 52.20 | 48.74 |