Income Taxes - Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Unrecognized tax benefits
Uncertain income tax positions not recognized, if percentage is less than, likelihood of being sustained	50.00%
U.S. federal statutory income tax rate and effective tax rate
U.S. federal statutory income tax rate (as a percent)	35.00%	35.00%	35.00%
State and local income taxes, net of U.S. federal income tax effect (as a percent)	5.20%	0.40%	5.50%
Foreign tax impact, net (as a percent)	6.20%	(7.20%)	(12.80%)
Deemed dividend on capital structure amendment (as a percent)		5.40%
Impact of deductible basis on the sale of energy research business ( as a percent)		(14.80%)
Reserves released upon tax settlement	18.60%
Non-deductible costs (as a percent)	(22.80%)	6.10%	0.90%
Other, net (as a percent)	(2.10%)	(0.40%)	(6.90%)
Effective income tax rate (as a percent)	40.10%	24.50%	21.70%
Earnings attributable to foreign subsidiaries not expected to be repatriated	$ 17,900
Tax liability if foreign subsidiary earnings were repatriated	3,000
Reconciliation of the beginning and ending amounts of unrecognized tax benefits
Balance, January 1	15,553	$ 14,395	$ 13,074
Additions based on tax positions related to the current year	66	2,807	309
Additions based on tax positions of prior years	406	349	3,681
Reductions for tax positions of prior years		(36)	(84)
Reductions due to settlements with taxing authorities	(2,153)	(1,773)	(1,108)
Reductions due to expiration of statute of limitations	(6,516)	(189)	(1,477)
Balance, December 31	7,356	15,553	14,395
Unrecognized tax benefits (net of federal benefits) if recognized will affect the entity's effective tax rate	6,900	14,600
Accrued interest expense related to tax reserves, net of related tax effects	2,200
Tax effect of interest accrued on unrecognized tax benefits	900
Net (reductions) additions of unrecognized tax-related interest expense	2,500	(100)	(800)
Penalties recognized, as a component of income tax expense	$ 0	$ 0	$ 0