Segment and Geographic Information - Identifiable Assets Table (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Identifiable assets:
Identifiable assets	$ 836.3	$ 919.2
United States
Identifiable assets:
Identifiable assets	747.4	821.7
Canada
Identifiable assets:
Identifiable assets	$ 88.9	$ 97.5