Statements Of Consolidated Common Stockholders' Equity (USD $) In Millions	Total	Common Stock [Member]	Treasury Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning Balance at Dec. 31, 2013	$ 5,886.6	$ 3.2	$ (48.6)	$ 4,690.1	$ 1,285.5	$ (43.6)
Net Income	266.2	0	0	0	266.2	0
Other comprehensive income, net of tax	1.1	0	0	0	0	1.1
Common stock dividends	(157.3)	0	0	0	(157.3)	0
Treasury stock acquired	(10.0)	0	(10.0)	0	0	0
Employee stock purchase plan	0.8	0	0	0.8	0	0
Long-term incentive plan	8.4	0	0	8.4	0	0
401(k) and profit sharing issuance	14.3	0	0	14.3	0	0
Dividend reinvestment plan	2.0	0	0	2.0	0	0
Ending Balance at Mar. 31, 2014	$ 6,012.1	$ 3.2	$ (58.6)	$ 4,715.6	$ 1,394.4	$ (42.5)