Net Income per Share - Basic and Diluted Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Earnings Per Share [Abstract]
Net income attributable to ION	$ 56,069	$ 1,188	$ 805	$ 77,167
Weighted average number of common shares outstanding (in shares)	164,693	164,063	164,630	163,956
Effect of dilutive stock awards (in shares)	19	360	21	287
Weighted average number of diluted common shares outstanding (in shares)	164,712	164,423	164,651	164,243
Basic net income per share (in dollars per share)	$ 0.34	$ 0.01	$ 0.00	$ 0.47
Diluted net income per share (in dollars per share)	$ 0.34	$ 0.01	$ 0.00	$ 0.47