Defined Benefit Pension Plans Fair Value of Plan Assets (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Defined benefit plan disclosure [Line Items]
Total carrying value	$ 3,758	$ 7,105
Fair value of plan assets	3,758	7,105	$ 11,509
Quoted prices in active markets, (level 1) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	6,208
Significant other observable inputs, (level 2) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	3,758	897
Significant unobservable inputs, (level 3) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
Money market funds
Defined benefit plan disclosure [Line Items]
Total carrying value	3,758	897
Money market funds | Quoted prices in active markets, (level 1) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets		0
Money market funds | Significant other observable inputs, (level 2) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	3,758	897
Money market funds | Significant unobservable inputs, (level 3) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
U.S. large-cap equities, growth [Member]
Defined benefit plan disclosure [Line Items]
Total carrying value	0	576
U.S. large-cap equities, growth [Member] | Quoted prices in active markets, (level 1) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets		576
U.S. large-cap equities, growth [Member] | Significant other observable inputs, (level 2) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
U.S. large-cap equities, growth [Member] | Significant unobservable inputs, (level 3) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
U.S. large-cap equities, value [Member]
Defined benefit plan disclosure [Line Items]
Total carrying value	0	542
U.S. large-cap equities, value [Member] | Quoted prices in active markets, (level 1) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets		542
U.S. large-cap equities, value [Member] | Significant other observable inputs, (level 2) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
U.S. large-cap equities, value [Member] | Significant unobservable inputs, (level 3) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
U.S. small/mid-cap equities, growth [Member]
Defined benefit plan disclosure [Line Items]
Total carrying value	0	246
U.S. small/mid-cap equities, growth [Member] | Quoted prices in active markets, (level 1) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets		246
U.S. small/mid-cap equities, growth [Member] | Significant other observable inputs, (level 2) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
U.S. small/mid-cap equities, growth [Member] | Significant unobservable inputs, (level 3) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
U.S. small/mid-cap equities, value [Member]
Defined benefit plan disclosure [Line Items]
Total carrying value	0	247
U.S. small/mid-cap equities, value [Member] | Quoted prices in active markets, (level 1) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets		247
U.S. small/mid-cap equities, value [Member] | Significant other observable inputs, (level 2) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
U.S. small/mid-cap equities, value [Member] | Significant unobservable inputs, (level 3) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
International equities, growth [Member]
Defined benefit plan disclosure [Line Items]
Total carrying value	0	376
International equities, growth [Member] | Quoted prices in active markets, (level 1) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets		376
International equities, growth [Member] | Significant other observable inputs, (level 2) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
International equities, growth [Member] | Significant unobservable inputs, (level 3) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
International equities, value [Member]
Defined benefit plan disclosure [Line Items]
Total carrying value	0	366
International equities, value [Member] | Quoted prices in active markets, (level 1) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets		366
International equities, value [Member] | Significant other observable inputs, (level 2) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
International equities, value [Member] | Significant unobservable inputs, (level 3) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
Fixed income
Defined benefit plan disclosure [Line Items]
Total carrying value	0	3,070
Fixed income | Quoted prices in active markets, (level 1) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets		3,070
Fixed income | Significant other observable inputs, (level 2) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
Fixed income | Significant unobservable inputs, (level 3) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
Multiclass world-allocation mutual funds
Defined benefit plan disclosure [Line Items]
Total carrying value	0	785
Multiclass world-allocation mutual funds | Quoted prices in active markets, (level 1) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets		785
Multiclass world-allocation mutual funds | Significant other observable inputs, (level 2) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
Multiclass world-allocation mutual funds | Significant unobservable inputs, (level 3) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0
Employee retirement plan [Member]
Defined benefit plan disclosure [Line Items]
Defined benefit plan, number of employees settled	905