CONSOLIDATED STATEMENTS OF CHANGES IN OWNERS' EQUITY (Unaudited) (USD $) In Millions, except Share data	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 Dec. 31, 2013	$ 0	$ 151.6	$ 20.5	$ (0.5)	$ (22.8)	$ 1,942.5	$ 2,091.3
Balance (in shares) at Dec. 31, 2013	42,162,000				367,000
Compensation on equity grants	0	1.6	0	0	0	2.6	4.2
Compensation on equity grants (in shares)	5,000				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)	(8,000)				8,000
Common stock and Partnership units tendered for tax withholding obligations	0	0	0	0	0	0	0
Common stock and Partnership units tendered for tax withholding obligations (in shares)	0				0
Sale of Partnership limited partner interests	0	0	0	0	0	115.3	115.3
Receivables from Partnership unit offerings		(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)
Dividends in excess of retained earnings	0	0	0	0	0	0	0
Distributions to noncontrolling interests	0	0	0	0	0	(81.7)	(81.7)
Other comprehensive income (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 Mar. 31, 2014	0	149.2	19.6	(0.8)	(23.6)	2,054.6	2,199.0
Balance (in shares) at Mar. 31, 2014	42,159,000				375,000
Balance at Dec. 31, 2014	0	164.9	25.5	4.8	(25.4)	2,369.7	2,539.5
Balance (in shares) at Dec. 31, 2014	42,143,000				389,000
Compensation on equity grants	0	2.1	0	0	0	3.8	5.9
Compensation on equity grants (in shares)	0				0
Accrual of distribution equivalent rights	0	(0.2)	0	0	0	0	(0.2)
Shares issued under compensation program	0	0	0	0	0	0	0
Shares issued under compensation program (in shares)	31,000				0
Common stock and Partnership units tendered for tax withholding obligations	0	0	0	0	(1.6)	(0.6)	(2.2)
Common stock and Partnership units tendered for tax withholding obligations (in shares)	(17,000)				17,000
Sale of Partnership limited partner interests	0	0	0	0	0	53.0	53.0
Receivables from Partnership unit offerings	0	(24.8)	0	0	0	0	(24.8)
Proceeds from equity issuances	0	336.2	0	0	0	0	336.2
Proceeds from equity issuances (in shares)	3,738,000				0
Impact of Partnership equity transactions	0	47.6	0	0	0	(47.6)	0
Dividends	0	0	(25.6)	0	0	0	(25.6)
Dividends in excess of retained earnings	0	(6.8)	0	0	0	3.4	(3.4)
Distributions to noncontrolling interests	0	0	0	0	0	(88.6)	(88.6)
Contributions from noncontrolling interests	0	0	0	0		0	0
Noncontrolling interest in acquired subsidiaries	0	0	0	0	0	303.9	303.9
Common stock issued in ATLS merger		1,013.6	0	0	0	0	1,013.6
Common stock issued in ATLS merger (in shares)	10,126,000				0
Issuance of Partnership units in APL merger	0	0	0	0	0	2,435.7	2,435.7
Other comprehensive income (loss)	0	0	0	0.5	0	16.2	16.7
Net income	0	0	3.2	0	0	31.4	34.6
Balance at Mar. 31, 2015	0.1	1,532.6	3.1	5.3	(27.0)	5,080.3	6,594.4
Balance (in shares) at Mar. 31, 2015	56,021,000				406,000
Balance at Feb. 28, 2015
Proceeds from equity issuances (in shares)	3,250,000
Balance at Mar. 31, 2015	$ 0.1
Balance (in shares) at Mar. 31, 2015	56,021,000