Operations and Summary of Significant Accounting Policies - Goodwill (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2015 USD ($) location	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Goodwill Impairment Testing
Goodwill	$ 123,950			$ 123,881	$ 123,881			$ 129,218	$ 123,881	$ 129,218	$ 129,218
Margin by which the reporting units passed the annual goodwill impairment test
Discount Rate Increases (as a percent)									4.80%
CAGR Decreases (as a percent)									1.05%
Goodwill [Roll Forward]
Goodwill at beginning of period, gross				147,961				152,768	$ 147,961	152,768
Accumulated impairment losses, beginning of period				(24,080)				(23,550)	(24,080)	(23,550)
Goodwill at the beginning of the period, net				$ 123,881				129,218	123,881	129,218
Goodwill acquired									2,070
Foreign exchange									(2,001)	(4,728)
Impairment	0	$ 0	$ 0		(38)	$ (492)	$ 0	0	0	(530)	0
Reclassifications										(79)
Goodwill at end of period, gross	148,031				147,961				148,031	147,961	152,768
Accumulated impairment losses, end of period	(24,081)				(24,080)				(24,081)	(24,080)	(23,550)
Goodwill at the end of the period, net	123,950				123,881				$ 123,950	123,881	129,218
Bierbach GmbH and Co KG
Goodwill [Roll Forward]
Impairment						$ (500)
United States
Goodwill Impairment Testing
Number of locations into which the activities will be consolidated | location									4
Australia
Goodwill Impairment Testing
Number of locations into which the activities will be consolidated | location									3
S&P Clever
Goodwill Impairment Testing
Number of locations into which the activities will be consolidated | location									8
Marginal percentage by which the company passed annual impairment test									9.00%
Goodwill	6,400								$ 6,400
Margin by which the reporting units passed the annual goodwill impairment test
Pre-Tax Operating Margin Decreases (as a percent)									40.00%
Goodwill [Roll Forward]
Goodwill at the end of the period, net	6,400								$ 6,400
North America
Goodwill Impairment Testing
Goodwill	85,834			$ 84,526	84,526			84,822	84,526	84,822	84,822
Goodwill [Roll Forward]
Goodwill at beginning of period, gross				95,192				95,488	95,192	95,488
Accumulated impairment losses, beginning of period				(10,666)				(10,666)	(10,666)	(10,666)
Goodwill at the beginning of the period, net				84,526				84,822	84,526	84,822
Goodwill acquired									1,860
Foreign exchange									(552)	(296)
Impairment									0
Reclassifications										0
Goodwill at end of period, gross	96,500				95,192				96,500	95,192	95,488
Accumulated impairment losses, end of period	(10,666)				(10,666)				(10,666)	(10,666)	(10,666)
Goodwill at the end of the period, net	85,834				84,526				85,834	84,526	84,822
Europe
Goodwill Impairment Testing
Goodwill	36,720			37,788	37,788			42,690	37,788	42,690	42,690
Goodwill [Roll Forward]
Goodwill at beginning of period, gross				51,202				55,574	51,202	55,574
Accumulated impairment losses, beginning of period				(13,414)				(12,884)	(13,414)	(12,884)
Goodwill at the beginning of the period, net				37,788				42,690	37,788	42,690
Goodwill acquired									210
Foreign exchange									(1,278)	(4,293)
Impairment										(530)
Reclassifications										(79)
Goodwill at end of period, gross	50,135				51,202				50,135	51,202	55,574
Accumulated impairment losses, end of period	(13,415)				(13,414)				(13,415)	(13,414)	(12,884)
Goodwill at the end of the period, net	36,720				37,788				36,720	37,788	42,690
Asia/Pacific
Goodwill Impairment Testing
Goodwill	1,396			1,567	1,567			1,706	1,567	1,706	1,706
Goodwill [Roll Forward]
Goodwill at beginning of period, gross				1,567				1,706	1,567	1,706
Accumulated impairment losses, beginning of period				0				0	0	0
Goodwill at the beginning of the period, net				$ 1,567				$ 1,706	1,567	1,706
Goodwill acquired									0
Foreign exchange									(171)	(139)
Impairment										0
Reclassifications										0
Goodwill at end of period, gross	1,396				1,567				1,396	1,567	1,706
Accumulated impairment losses, end of period	0				0				0	0	0
Goodwill at the end of the period, net	$ 1,396				$ 1,567				$ 1,396	$ 1,567	$ 1,706