CONSOLIDATED STATEMENTS OF CHANGES IN OWNERS' EQUITY (Unaudited) (USD $) In Millions, except Share data in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings (Accumulated Deficit) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Shares [Member]	Noncontrolling Interests [Member]	Total
Balance at beginning of period at Dec. 31, 2012	$ 0	$ 184.4	$ (32.0)	$ 1.2	$ (9.5)	$ 1,609.3	$ 1,753.4
Balance at beginning of period (in shares) at Dec. 31, 2012	42,295				198
Compensation on equity grants	0	2.1	0	0	0	1.7	3.8
Compensation on equity grants (in shares)	35				0
Accrual of distribution equivalent rights						(0.3)	(0.3)
Sale of Partnership limited partner interests	0	0	0	0	0	105.3	105.3
Impact of Partnership equity transactions	0	6.3	0	0	0	(6.3)	0
Dividends	0	(19.4)	0	0	0	0	(19.4)
Distributions	0	0	0	0	0	(61.7)	(61.7)
Other comprehensive loss	0	0	0	(1.1)	0	(10.6)	(11.7)
Net income	0	0	13.4	0	0	20.4	33.8
Balance at end of period at Mar. 31, 2013	0	173.4	(18.6)	0.1	(9.5)	1,657.8	1,803.2
Balance end of period (in shares) at Mar. 31, 2013	42,330				198
Balance at beginning of period at Dec. 31, 2013	0	151.6	20.5	(0.5)	(22.8)	1,942.5	2,091.3
Balance at beginning of period (in shares) at Dec. 31, 2013	42,162				367
Compensation on equity grants	0	1.6	0	0	0	2.6	4.2
Compensation on equity grants (in shares)	5				0
Accrual of distribution equivalent rights	0	0	0	0	0	(0.6)	(0.6)
Repurchase of common stock	0	0	0	0	(0.8)	0	(0.8)
Repurchase of common stock (in shares)	(8)				8
Sale of Partnership limited partner interests	0	0	0	0	0	115.3	115.3
Receivables from unit offerings	0	(5.9)	0	0	0	0	(5.9)
Impact of Partnership equity transactions	0	7.1	0	0	0	(7.1)	0
Dividends	0	(5.2)	(20.5)	0	0	0	(25.7)
Distributions	0	0	0	0	0	(81.7)	(81.7)
Other comprehensive loss	0	0	0	(0.3)	0	(3.7)	(4.0)
Net income	0	0	19.6	0	0	87.3	106.9
Balance at end of period at Mar. 31, 2014	$ 0	$ 149.2	$ 19.6	$ (0.8)	$ (23.6)	$ 2,054.6	$ 2,199.0
Balance end of period (in shares) at Mar. 31, 2014	42,159				375