Share Based Compensation (Details 1) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011
Restricted stock units payable in Stock [Member]
Restricted stock units
Outstanding at the beginning of year, nonvested	762
Grants in periods, number of shares	373
Vested in periods, number of shares	(393)
Forfeited RSU's, number of shares	(104)
Outstanding at the end of year, nonvested	638
Outstanding at the beginning of year, weighted average grant date fair value	$ 47.55
Grants in periods, weighted average grant date fair value	$ 25.27
Vested in periods, weighted average grant date fair value	$ (47.36)
Forfeited RSU's, weighted average grant date fair value	$ (42.14)
Outstanding at the end of year, weighted average grant date fair value	$ 35.53
Restricted Stock Units Payable in Cash [Member]
Restricted stock units
Outstanding at the beginning of year, nonvested	3,472
Grants in periods, number of shares	695
Vested in periods, number of shares	(863)
Forfeited RSU's, number of shares	(377)
Outstanding at the end of year, nonvested	2,927
Outstanding at the beginning of year, weighted average grant date fair value	$ 14.60
Grants in periods, weighted average grant date fair value	$ 26.05
Vested in periods, weighted average grant date fair value	$ (13.94)
Forfeited RSU's, weighted average grant date fair value	$ (15.94)
Outstanding at the end of year, weighted average grant date fair value	$ 17.33