Description of the period of time over which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, which may be expressed in a variety of ways (for example, in years, month and year).

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod
Namespace Prefix:	us-gaap
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration

Stock-Based Compensation (Details) (USD $)			6 Months Ended
Stock-Based Compensation (Details) (USD $)	Jun. 30, 2011	May 03, 2011	Jun. 30, 2011 Stock Options [Member]	Jun. 30, 2011 Performance-Vesting Share (PVS) Awards [Member]
Stock-Based Compensation, by Type of Award [Line Items]
Shares available for issuance under the 2011 Plan (in shares)	4,735,429	4,800,000
Granted (in shares)			471,468
Weighted average exercise price (per share)			$ 40.85
Vesting period (in years)			Four	Three
Expiration period (in years)			Ten
Weighted average grant date fair value (per share)			$ 8.76
Assumptions used in Black-Scholes model
Risk-free interest rate			2.16%
Expected life (in years)			5.5
Stock volatility			24.30%
Dividend yield			1.70%
Number of shares of common stock per PVS award (in shares)				1
PVS payout, Minimum				0.00%
PVS payout, Maximum				200.00%
Granted, PVS awards (in shares)				101,099
Weighted average grant-date fair value (per share)				$ 40.85
Reduction in number of shares available for issuance, stock option and stock appreciation rights				one share for each award granted
Reduction in number of shares available for issuance, all other awards				2.35 times the number of shares awarded