Defined Benefit Pension Plans Fair Value of Plan Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined benefit plan disclosure [Line Items]
Total carrying value	$ 11,509	$ 15,216
Fair value of plan assets	11,509	15,216	$ 21,567
Quoted prices in active markets, (level 1) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	8,627	12,422
Significant other observable inputs, (level 2) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	2,882	2,794
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	2,882	2,794
Money market funds | Quoted prices in active markets, (level 1) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	0	0
Money market funds | Significant other observable inputs, (level 2) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	2,882	2,794
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	687	1,869
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	687	1,869
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	729	1,492
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	729	1,492
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	339	781
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	339	781
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	339	1,003
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	339	1,003
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	443	1,270
International equities, growth [Member] | Quoted prices in active markets, (level 1) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	443	1,270
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	514	1,183
International equities, value [Member] | Quoted prices in active markets, (level 1) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	514	1,183
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	4,669	3,035
Fixed income | Quoted prices in active markets, (level 1) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	4,669	3,035
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	907	1,789
Multiclass world-allocation mutual funds | Quoted prices in active markets, (level 1) [Member]
Defined benefit plan disclosure [Line Items]
Fair value of plan assets	907	1,789
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