Business Segments (Data by Geographic Region) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 297,285	$ 221,714	$ 200,370	$ 177,413	$ 311,983	$ 228,614	$ 196,017	$ 196,052	$ 896,782	$ 932,666	$ 873,364
Long-lived assets	187,896				252,388				187,896	252,388	203,175
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									779,890	813,609	746,800
Long-lived assets	182,116				246,902				182,116	246,902	197,141
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									116,892	119,057	126,564
Long-lived assets	5,780				5,486				5,780	5,486	6,034
HBB
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	204,818	135,155	118,385	101,325	192,889	134,099	114,651	106,151	559,683	547,790	521,567
NACoal
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 33,210	$ 49,840	$ 49,780	$ 39,872	$ 46,067	$ 52,870	$ 43,567	$ 51,147	$ 172,702	$ 193,651	$ 132,367