Share-Based Compensation - Stock Options (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012 years
Options outstanding and exercisable under the Company's 1991 Equity and Performance Incentive Plan
Outstanding, Shares, Beginning balance	3,201
Outstanding, Weighted average exercise price, Beginning balance	$ 36.70
Expired or forfeited, Shares	(400)
Expired or forfeited, Weighted average exercise price	$ 36.70
Exercised, Shares	(331)
Exercised, Weighted average exercise price	$ 29.93
Granted, Shares	539
Granted, Weighted average exercise price	$ 34.89
Outstanding, Shares, Ending balance	3,009
Outstanding, Weighted average exercise price, Ending balance	$ 37.12
Outstanding, Weighted Average Remaining Contractual Term	6
Outstanding, Aggregate Intrinsic Value	$ 13,856	[1]
Options exercisable, Shares	1,910
Options exercisable, Weighted average exercise price	$ 39.76
Option exercisable, Weighted average remaining contractual term	4
Option exercisable, aggregate Intrinsic Value	7,265	[1]
Options vested and expected to vest, Shares	2,982	[2]
Options vested and expected to vest, Weighted average exercise price	$ 37.16	[2]
Options vested and expected to vest, Weighted average remaining contractual term	6	[2]
Options vested and expected to vest, aggregate intrinsic value	$ 13,697	[1],[2]

[1] The aggregate intrinsic value (the difference between the closing price of the Company’s common shares on the last trading day of the first quarter of 2012 and the exercise price, multiplied by the number of “in-the-money” options) that would have been received by the option holders had all option holders exercised their options on March 31, 2012. The amount of aggregate intrinsic value will change based on the fair market value of the Company’s common shares.

[2] The options expected to vest are the result of applying the pre-vesting forfeiture rate assumption to total outstanding non-vested options.