Retirement Plans (Fair Values of Qualified Plan's Assets) (Details) - USD ($)
$ in Thousands

Cash and cash equivalents are comprised of commercial paper, short-term bills and notes, and short-term investment funds, which are valued at quoted prices in active markets for similar securities.

U.S. equity securities are comprised of investments in common stock of U.S. companies for total return purposes. These investments are valued by the trustee at closing prices from national exchanges on the valuation date.

Certain investments that are measured at fair value using the net asset value per share (or its equivalent) practical expedient have not been categorized in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the statement of financial position.

International equity securities are comprised of investments in common stock of companies located outside of the U.S for total return purposes. These investments are valued by the trustee at closing prices from national exchanges on the valuation date, or the values are adjusted as a result of market movements following the close of local trading using inputs to models that are observable either directly or indirectly. The portion of these investments that are measured at fair value using the net asset value per share practical expedient (see note 4 below) can be redeemed on a monthly basis.

Investment grade fixed income consists of debt obligations either issued by the US government or have a rating of BBB- / Baa or higher assigned by a major credit rating agency. These investments are valued based on unadjusted quoted market prices (Level 1), or based on quoted prices in inactive markets, or whose values are based on models, but the inputs to those models are observable either directly or indirectly (Level 2).

High yield fixed income consists primarily of debt obligations that have a rating of below BBB- / Baa or lower assigned by a major credit rating agency. These investments are valued based on unadjusted quoted market prices.

Alternative investments consist primarily of an investment in asset classes other than stocks, bonds, and cash. Alternative investments can include commodities, hedge funds, private equity, managed futures, and derivatives. These investments are valued based on unadjusted quoted market prices and can be redeemed on a bi-monthly basis.

Real estate is investments in a real estate collective trust for purposes of total return. These investments are valued based on prices or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. These investments can be redeemed on a quarterly basis.