Income Taxes - Summary of Federal Net Operating Loss Carryforwards and Related Deferred Income Tax Aseets (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Income Tax Contingency [Line Items]
Deferred Tax Assets, Net Operating Loss Carryforwards	$ 100.7	$ 98.1
Federal [Member]
Income Tax Contingency [Line Items]
Net Operating Loss Carryforwards	269.6
Deferred Tax Assets, Net Operating Loss Carryforwards	94.4	91.2
State and Local Jurisdiction [Member]
Income Tax Contingency [Line Items]
Deferred Tax Assets, Net Operating Loss Carryforwards	6.3	6.9
2017 through 2020 [Member] | Federal [Member]
Income Tax Contingency [Line Items]
Net Operating Loss Carryforwards	109.0
Deferred Tax Assets, Net Operating Loss Carryforwards	38.2
2021 through 2025 [Member] | Federal [Member]
Income Tax Contingency [Line Items]
Net Operating Loss Carryforwards	53.6
Deferred Tax Assets, Net Operating Loss Carryforwards	18.8
2026 through 2030 [Member] | Federal [Member]
Income Tax Contingency [Line Items]
Net Operating Loss Carryforwards	32.1
Deferred Tax Assets, Net Operating Loss Carryforwards	11.2
2031 through 2032 [Member] | Federal [Member]
Income Tax Contingency [Line Items]
Net Operating Loss Carryforwards	74.9
Deferred Tax Assets, Net Operating Loss Carryforwards	$ 26.2