Property, Plant, and Equipment (Details Textual) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Future minimum rent expense on non-Leasing Group leases
Gains on disposition of flood-damaged property, plant and equipment	$ 0.4	$ 17.6	$ 9.7
Net book value of non operating plants	7.4
Non-Leasing Group
Future minimum rent expense on non-Leasing Group leases
2013	3.9
2014	2.7
2015	2.0
2016	1.3
2017	0.7
Thereafter	1.2
Missouri
Future minimum rent expense on non-Leasing Group leases
Payments from insurance carriers		35.0
Payments pertaining to replacement or repairs of damaged property plant and equipment		22.7
Net book value of damaged property, plant and equipment		5.7
Gains on disposition of flood-damaged property, plant and equipment	0.4	17.0
Tennessee
Future minimum rent expense on non-Leasing Group leases
Payments from insurance carriers			27.5
Payments pertaining to replacement or repairs of damaged property plant and equipment			12.6
Net book value of damaged property, plant and equipment			2.3
Gains on disposition of flood-damaged property, plant and equipment		$ 0.6	$ 9.7