Income Taxes (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2009	Dec. 31, 2008	Dec. 31, 2007	Jun. 08, 2010
Income Taxes (Textual) [Abstract]
Effective tax rate	13.20%	21.40%
Net benefit for a previously unrecognized position	$ 33.0
Expense for non-income based state taxes	10.0
Proposed deduction disallowance by tax authorities			130	130	130
Notice of Assessment of corporate excise tax including penalties and interest						$ 103.5