CONSOLIDATED STATEMENTS OF EQUITY (USD $) In Millions, unless otherwise specified	Total	Total Common Shareholders' Equity	Shares in Deferred Compensation Trust	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Preferred Stock of Subsidiary	Noncontrolling Interest in Subsidiaries
Balance at Dec. 31, 2011	$ 3,012.6	$ 2,961.4	$ (17.1)	$ 78.3	$ 2,579.1	$ 363.6	$ (42.5)	$ 51.1	$ 0.1
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributed to common shareholders	281.2	281.4	0	0	0	281.4	0	0	(0.2)
Other comprehensive income (loss)	1.6	1.6	0	0	0	0	1.6	0	0
Stock-based compensation	(4.8)	(4.8)	0	0	(4.1)	(0.7)	0	0	0
Dividends on common stock (dividends per common share of $2.72)	(211.9)us-gaap_DividendsCommonStockCash	(211.9)	0	0	0	(211.9)	0	0	0
Shares issued to and purchased for the deferred compensation trust	(3.2)	(3.2)	(3.2)	0	0	0	0	0	0
Other	1.3us-gaap_StockholdersEquityOther	1.3	2.6	0	(0.4)	(0.9)	0	0	0
Balance at Dec. 31, 2012	3,076.8	3,025.8	(17.7)	78.3	2,574.6	431.5	(40.9)	51.1	(0.1)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributed to common shareholders	351.7	351.8	0	0	0	351.8	0	0	(0.1)
Other comprehensive income (loss)	17.7	17.7	0	0	0	0	17.7	0	0
Issuance of common stock	79.8	79.8	0	1.5	78.3	0	0	0	0
Stock-based compensation	0.3	0.3	0	0	1.0	(0.7)	0	0	0
Dividends on common stock (dividends per common share of $2.72)	(214.6)us-gaap_DividendsCommonStockCash	(214.6)	0	0	0	(214.6)	0	0	0
Net contributions from noncontrolling parties	1.0	0	0	0	0	0	0	0	1.0
Shares issued to and purchased for the deferred compensation trust	0	0	(6.3)	0.1	6.2	0	0	0	0
Other	0.7us-gaap_StockholdersEquityOther	0.5	1.0	0	0.4	(0.9)	0	0	0.2
Balance at Dec. 31, 2013	3,313.4	3,261.3	(23.0)	79.9	2,660.5	567.1	(23.2)	51.1	1.0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income attributed to common shareholders	276.8	276.9	0	0	0	276.9	0	0	(0.1)
Other comprehensive income (loss)	(4.4)	(4.4)	0	0	0	0	(4.4)	0	0
Issuance of common stock	2.4	2.4	0	0.1	2.3	0	0	0	0
Stock-based compensation	(21.7)	(21.7)	0	0	(20.9)	(0.8)	0	0	0
Dividends on common stock (dividends per common share of $2.72)	(216.3)us-gaap_DividendsCommonStockCash	(216.3)	0	0	0	(216.3)	0	0	0
Shares issued to and purchased for the deferred compensation trust	(0.6)	(0.6)	(0.6)	0	0	0	0	0	0
Other	1.2us-gaap_StockholdersEquityOther	2.1	2.7	0	0.3	(0.9)	0	0	(0.9)
Balance at Dec. 31, 2014	$ 3,350.8	$ 3,299.7	$ (20.9)	$ 80.0	$ 2,642.2	$ 626.0	$ (27.6)	$ 51.1	$ 0

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Value of shares purchased for or issued to the deferred compensation trust.

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.

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