Share-Based Awards (Details - Options) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
The activity related to the Company's share options as follows:
Outstanding at beginning of year	1,936,095
Granted	123,162	91,817	598,698
Exercised	(194,201)	(860,154)	(250,400)
Forfeited or expired	(1,900)
Outstanding at end of year	1,863,156	1,936,095
Exercisable at end of year	1,856,435
Vested and expected to vest at end of year	1,862,867
The weighted average exercise price is as follows:
Outstanding at beginning of year	$ 61.86
Granted	$ 68.59
Exercised	$ 56.19
Forfeited or expired	$ 65.05
Outstanding at end of year	$ 62.89	$ 61.86
Exercisable at end of year	$ 62.84
Vested and expected to vest at end of year	$ 62.89
Summary Of Option Activity [Abstract]
Weighted average grant date fair value of options granted	$ 7.43	$ 10.29	$ 7.95
Total intrinsic value of options exercised	$ 4.6	$ 21.0	$ 5.0
Proceeds from options exercised	10.6	37.2	12.7
Weighted average remaining contractual term	3.6
Aggregate intrinsic value of options outstanding, exercisable, vested and expected to vest	$ 7.4
Expected life of replacement awards issued as part of the acquisition of Paris Re			3
Expected life of share option awards other than replacement awards issued as a part of the acquisition of Paris Re			6