Business Segments (Data by Geographic Region) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 311,983	$ 228,614	$ 196,017	$ 196,052	$ 318,183	$ 210,067	$ 171,435	$ 173,679	$ 932,666	$ 873,364	$ 790,455
Long-lived assets	252,388				203,175				252,388	203,175	129,234
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									813,609	746,800	662,061
Long-lived assets	246,902				197,141				246,902	197,141	124,236
Other
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues									119,057	126,564	128,394
Long-lived assets	5,486				6,034				5,486	6,034	4,998
HBB
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	192,889	134,099	114,651	106,151	181,131	124,820	110,676	104,940	547,790	521,567	493,047
NACoal
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenues	$ 46,067	$ 52,870	$ 43,567	$ 51,147	$ 50,822	$ 38,012	$ 19,199	$ 24,334	$ 193,651	$ 132,367	$ 81,766