Employee Benefit Plans (Details 8)	12 Months Ended
	Dec. 31, 2012
Fixed income investments - Cash/money market account
Investment Category Benchmark	Citigroup Treasury Bill Index - 3 month
Range of acceptable deviation from investment category benchmark, minimum	0.00%
Range of acceptable deviation from investment category benchmark, maximum	0.50%
Fixed income investments - US government bond fund
Investment Category Benchmark	Barclays Intermediate Government Bond Index
Range of acceptable deviation from investment category benchmark, minimum	0.00%
Range of acceptable deviation from investment category benchmark, maximum	2.00%
Fixed income investments - US corporate bond fund
Investment Category Benchmark	Barclays Aggregate Index
Range of acceptable deviation from investment category benchmark, minimum	0.00%
Range of acceptable deviation from investment category benchmark, maximum	2.00%
Fixed income investments - US corporate high yield bond fund
Investment Category Benchmark	Barclays High Yield Index
Range of acceptable deviation from investment category benchmark, minimum	0.00%
Range of acceptable deviation from investment category benchmark, maximum	2.00%
Equity investments - Large cap value fund
Investment Category Benchmark	Russell 1000 Value Index
Range of acceptable deviation from investment category benchmark, minimum	0.00%
Range of acceptable deviation from investment category benchmark, maximum	3.00%
Equity investments - Large cap growth fund
Investment Category Benchmark	Russell 1000 Growth Index
Range of acceptable deviation from investment category benchmark, minimum	0.00%
Range of acceptable deviation from investment category benchmark, maximum	3.00%
Equity investments - Mid cap equity fund
Investment Category Benchmark	Russell Mid Cap Index
Range of acceptable deviation from investment category benchmark, minimum	0.00%
Range of acceptable deviation from investment category benchmark, maximum	3.00%
Equity investments - Small cap growth fund
Investment Category Benchmark	Russell 2000 Growth Index
Range of acceptable deviation from investment category benchmark, minimum	0.00%
Range of acceptable deviation from investment category benchmark, maximum	3.00%
Equity investments - Foreign equity fund
Investment Category Benchmark	MSCI EAFE Index
Range of acceptable deviation from investment category benchmark, minimum	0.00%
Range of acceptable deviation from investment category benchmark, maximum	3.00%
Equity investments - Company stock
Investment Category Benchmark	Russell 2000 Index
Range of acceptable deviation from investment category benchmark, minimum	0.00%
Range of acceptable deviation from investment category benchmark, maximum	3.00%