Other Assets (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Other Assets [Abstract]
Other, net of accumulated amortization of $5.1 and $3.1 at September 30, 2016 and December 31, 2015, respectively	$ 56.5	$ 40.4
Deferred tax asset, net	32.8	22.2
Goodwill	23.9	23.9
Prepaid expenses	14.2	10.1
Hedge assets	8.5	30.9
Marketable securities	5.4	4.3
Deposits	2.2	4.2
Other Assets	256.3	267.2
Accumulated amortization, other	5.1	3.1
Investments in and advances to consolidated subsidiaries	$ 0.0	0.0
KWE [Member]
Other Assets [Abstract]
Shares in KWE (in shares)	29.6
Share price	$ 13.02
KWE [Member] | Equity Securities [Member]
Other Assets [Abstract]
Investments in and advances to consolidated subsidiaries	$ 385.0
Investment cost basis	486.7
Furniture and Fixtures [Member]
Other Assets [Abstract]
Office furniture and equipment net of accumulated depreciation of $22.5 and $14.0 at September 30, 2016 and December 31, 2015, respectively	25.9	27.9
Accumulated amortization, office furniture and equipment	22.5	14.0
Above Market Leases [Member]
Other Assets [Abstract]
Above-market leases, net of accumulated amortization of $27.5 and $19.6 at September 30, 2016 and December 31, 2015, respectively	86.9	103.3
Accumulated amortization, above-market leases	$ 27.5	$ 19.6