Summary Of Significant Accounting Policies Summary of Significant Accounting Policies (Summary of Nonvested Shares Related To Long-Term Incentive Plan) (Details) - $ / shares		9 Months Ended
		Sep. 30, 2015	Dec. 31, 2014
Weighted-average Fair Value per Unit at Grant Date
Closing common share price			$ 46.13
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Three-year risk-free rate		1.10%
Volatility rate, minimum		12.00%
Volatility rate, maximum		18.00%
Share Units
Share Units, Nonvested as of beginning of year		1,162,377
Share Units, Granted	[1]	569,892
Share Units, Forfeitures		(1,944)
Share Units, Vested	[2]	(92,892)
Share Units, Nonvested as of Current period end		1,637,433
Weighted-average Fair Value per Unit at Grant Date
Weighted-average Fair Value per Unit, Nonvested as of Beginning of year		$ 35.35
Weighted-average Fair Value per Unit, Grants	[1]	52.88
Weighted-average Fair Value per Unit, Forfeitures		34.75
Weighted-average Fair Value per Unit, Vested	[2]	45.97
Weighted-average Fair Value per Unit, Nonvested as of Current period end		$ 40.85
Performance period		3 years
Risk free interest rate period		3 years

[1] Performance share units granted to certain executive and nonexecutive officers and other eligible employees in 2015 under the 2014 Incentive Plan.

[2] (b)Performance share units vested due to the attainment of retirement eligibility by certain employees. Actual shares issued for retirement-eligible employees will vary depending on actual performance over the three-year measurement period.