Employee Benefit Plans (Details 10)	Dec. 31, 2011	Dec. 31, 2010
Summary of weighted-average asset allocations
Weighted average asset allocations	100.00%	100.00%
U.S. equity [Member]
Summary of weighted-average asset allocations
Weighted average asset allocations	33.60%	33.10%
International equity [Member]
Summary of weighted-average asset allocations
Weighted average asset allocations	24.40%	28.50%
Fixed income [Member]
Summary of weighted-average asset allocations
Weighted average asset allocations	41.20%	36.80%
Money market/cash/guaranteed investment contracts [Member]
Summary of weighted-average asset allocations
Weighted average asset allocations	0.80%	1.60%