Leases (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Leases [Abstract]
Percentage of ownership interest	100.00%
Rent expense	$ 5.9	$ 5.4	$ 6.3
Rent expense associated with related party lease agreements	1.8	1.9	2.0
Non-cancelable payments due to related parties, year one	1.7
Non-cancelable payments due to related parties, year two	1.7
Non-cancelable payments due to related parties, year three	1.7
Non-cancelable payments due to related parties, year four	1.7
Non-cancelable payments due to related parties year five	1.7
Non-cancelable payments due to related parties, thereafter	$ 1.7