CONSOLIDATED STATEMENTS OF CHANGES IN OWNERS' EQUITY (Unaudited) (USD $) In Millions, except Share data in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Shares [Member]	Noncontrolling Interests [Member]	Total
Balance at beginning of period at Dec. 31, 2011	$ 0	$ 229.5	$ (70.1)	$ (1.3)	$ 0	$ 1,172.6	$ 1,330.7
Balance at beginning of period (in shares) at Dec. 31, 2011	42,398				0
Compensation on equity grants	0	3.9	0	0	0	0.6	4.5
Compensation on equity grants (in shares)	43				0
Sale of Partnership limited partner interests	0	0	0	0	0	115.2	115.2
Impact of Partnership equity transactions	0	(18.3)	0	0	0	18.3	0
Dividends	0	(14.3)	0	0	0	(0.1)	(14.4)
Distributions to owners	0	0	0	0	0	(54.3)	(54.3)
Other comprehensive income (loss)	0	0	0	1.3	0	13.1	14.4
Net income	0	0	9.6	0	0	59.6	69.2
Balance at end of period at Mar. 31, 2012	0	200.8	(60.5)	0	0	1,325.0	1,465.3
Balance end of period (in shares) at Mar. 31, 2012	42,441				0
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	0	0	0	0	(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 to owners	0	0	0	0	0	(61.7)	(61.7)
Other comprehensive income (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