CONDENSED CONSOLIDATED INCOME STATEMENTS - USD ($) shares in Millions, $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Operating revenues	$ 2,377.4	$ 2,286.5
Operating expenses
Cost of sales	1,009.6	972.1
Other operation and maintenance	550.6	511.9
Depreciation and amortization	226.4	208.6
Property and revenue taxes	48.0	48.8
Total operating expenses	1,834.6	1,741.4
Operating income	542.8	545.1
Equity in earnings of transmission affiliates	36.1	32.8
Other income, net	30.9	7.5
Interest expense	124.4	106.7
Other expense	(57.4)	(66.4)
Income before income taxes	485.4	478.7
Income tax expense	65.0	88.3
Net income	420.4	390.4
Preferred stock dividends of subsidiary	0.3	0.3
Net income attributed to common shareholders	$ 420.1	$ 390.1
Earnings per share
Basic (in dollars per share)	$ 1.33	$ 1.24
Diluted (in dollars per share)	$ 1.33	$ 1.23
Weighted average common shares outstanding
Basic (in shares)	315.5	315.5
Diluted (in shares)	316.7	316.9

The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.

Name:	us-gaap_CostOfGoodsAndServicesSold
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.