Derivative Financial Instruments (Summary Of Outstanding Fair Value Hedges) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Derivative [Line Items]
Derivative, notional amount	$ 23,224.1	$ 13,778.4
Interest Rate Swaps [Member]
Derivative [Line Items]
Derivative, notional amount	1,385.0	1,185.0
Interest Rate Swaps [Member] | Expiration Date August 15, 2020 [Member] | Interest Rate Received 4.350% [Member] | 2015 [Member]
Derivative [Line Items]
Derivative, notional amount	$ 200.0	0.0
Interest Rate Received	4.35%
Expiration Date	Aug. 15, 2020
Interest Rate Swaps [Member] | Expiration Date August 15, 2020 [Member] | Interest Rate Received 4.350% [Member] | 2014 [Member]
Derivative [Line Items]
Derivative, notional amount	$ 150.0	150.0
Interest Rate Received	4.35%
Expiration Date	Aug. 15, 2020
Interest Rate Swaps [Member] | Expiration Date August 15, 2020 [Member] | Interest Rate Received 4.350% [Member] | 2013 [Member]
Derivative [Line Items]
Derivative, notional amount	$ 10.0	10.0
Interest Rate Received	4.35%
Expiration Date	Aug. 15, 2020
Interest Rate Swaps [Member] | Expiration Date August 15, 2020 [Member] | Interest Rate Received 4.350% [Member] | 2012 [Member]
Derivative [Line Items]
Derivative, notional amount	$ 200.0	200.0
Interest Rate Received	4.35%
Expiration Date	Aug. 15, 2020
Interest Rate Swaps [Member] | Expiration Date January 15, 2018 [Member] | Interest Rate Received 1.875% [Member] | 2012 [Member]
Derivative [Line Items]
Derivative, notional amount	$ 625.0	625.0
Interest Rate Received	1.875%
Expiration Date	Jan. 15, 2018
Interest Rate Swaps [Member] | Expiration Date February 15, 2017 [Member] | Interest Rate Received 2.375% [Member] | 2012 [Member]
Derivative [Line Items]
Derivative, notional amount	$ 200.0	$ 200.0
Interest Rate Received	2.375%
Expiration Date	Feb. 15, 2017