Goodwill and Other Intangible Assets - Other Intangible Assets (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012	Dec. 31, 2011
Details of other intangible assets
Acquisition Costs	$ 51.0	$ 45.1
Accumulated Amortization	8.7	7.0
Net	42.3	38.1
Goodwill	53.8	49.7	9.5
Total	107.6	99.3
Tradenames [Member]
Details of other intangible assets
Indefinite-lived tradenames	11.5	11.5
Non-contractual customer relationships [Member]
Details of other intangible assets
Acquisition Costs	47.3	41.7
Accumulated Amortization	7.2	5.7
Net	40.1	36.0
Other [Member]
Details of other intangible assets
Acquisition Costs	3.7	3.4
Accumulated Amortization	1.5	1.3
Net	$ 2.2	$ 2.1