Employee Benefit Plans (Investment Strategies) (Details)	12 Months Ended
	Dec. 31, 2015
Small-Cap Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset Category	Small-cap fund
Fund's Investment Strategy	Seeks to track performance of the Center for Research in Security Prices ("CRSP") US Small Cap Index
Mid-Cap Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset Category	Mid-cap fund
Fund's Investment Strategy	Seeks to track performance of the CRSP US Mid Cap Index
Large-Cap Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset Category	Large-cap funds
Fund's Investment Strategy	Seeks to track performance of the Standard & Poor’s 500 Index
International Equity Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset Category	International equity fund
Fund's Investment Strategy	Seeks long-term growth of capital by investing 65% or more of assets in international equities
Short-Term Bond Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset Category	Short-term bond funds
Fund's Investment Strategy	Seeks current income with limited price volatility through investment in primarily high quality bonds
Intermediate-Term Bond Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset Category	Intermediate-term bond funds
Fund's Investment Strategy	Seeks moderate and sustainable level of current income by investing primarily in high quality fixed income securities with maturities from five to ten years
Long-Term Investment Grade Bond Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset Category	Long-term investment grade bond funds
Fund's Investment Strategy	Seeks high and sustainable current income through investment primarily in long-term high grade bonds
Short-Term Investment Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset Category	Short-term investment funds
Fund's Investment Strategy	Invests primarily in high quality commercial paper and government securities
Group Annuity Contract [Member]
Defined Benefit Plan Disclosure [Line Items]
Asset Category	Group annuity contract
Fund's Investment Strategy	Guarantees a specified return based on a specified index