Employee Benefit Plans (Expected long-term return by asset category) (Details)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Expected Long Term Return [Abstract]
Expected long-term return	5.60%	6.60%
Assets allocation [Abstract]
Assets allocation	100.00%
Cash and Cash Equivalents [Member]
Expected Long Term Return [Abstract]
Expected long-term return	0.50%
Assets allocation [Abstract]
Assets allocation	0.60%
Equity Securities [Member]
Expected Long Term Return [Abstract]
Expected long-term return	7.00%
Assets allocation [Abstract]
Assets allocation	42.30%
Debt Securities [Member]
Expected Long Term Return [Abstract]
Expected long-term return	4.00%
Assets allocation [Abstract]
Assets allocation	45.30%
Target Return Funds [Member]
Expected Long Term Return [Abstract]
Expected long-term return	7.00%
Assets allocation [Abstract]
Assets allocation	11.80%