Retirement Plans (Fair Value of Plan Assets by Fair Value Level) (Details) - Pension Plan - USD ($)	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 128,352,000	$ 145,901,000	$ 132,751,000
Fair Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	128,352,000	145,901,000
Quoted Prices In Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	127,805,000	145,353,000
Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	547,000	548,000
Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Cash | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8,770,000	5,238,000
Cash | Quoted Prices In Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8,770,000	5,238,000
Cash | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Cash | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
U.S. large- and mid-cap stocks
Defined Benefit Plan Disclosure [Line Items]
Minimum market capitalization for investments	3,000,000,000
U.S. large- and mid-cap stocks | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	63,823,000	68,909,000
U.S. large- and mid-cap stocks | Quoted Prices In Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	63,823,000	68,909,000
U.S. large- and mid-cap stocks | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
U.S. large- and mid-cap stocks | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
U.S. small-cap mutual funds | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,713,000	5,377,000
U.S. small-cap mutual funds | Quoted Prices In Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,713,000	5,377,000
U.S. small-cap mutual funds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
U.S. small-cap mutual funds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International large-cap mutual funds | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11,091,000	18,341,000
International large-cap mutual funds | Quoted Prices In Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11,091,000	18,341,000
International large-cap mutual funds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
International large-cap mutual funds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Emerging markets mutual funds | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,439,000	7,363,000
Emerging markets mutual funds | Quoted Prices In Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,439,000	7,363,000
Emerging markets mutual funds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Emerging markets mutual funds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
U.S. Treasury and government sponsored agency bonds and notes | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	547,000	548,000
U.S. Treasury and government sponsored agency bonds and notes | Quoted Prices In Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
U.S. Treasury and government sponsored agency bonds and notes | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	547,000	548,000
U.S. Treasury and government sponsored agency bonds and notes | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Mutual funds | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	32,969,000	40,046,000
Mutual funds | Quoted Prices In Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	32,969,000	40,046,000
Mutual funds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Mutual funds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	0
Other | Fair Value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		79,000
Other | Quoted Prices In Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		79,000
Other | Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0
Other | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 0