Significant Accounting Policies - Schedule of Basic Weighted Average Shares Reconciles to Diluted Weighted Average Shares Outstanding (Details) - shares shares in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Basic weighted average common shares outstanding	76,283	76,309	76,220	76,115	75,955	75,819	75,690	75,749	76,232	75,803	77,126
Dilutive effect of stock options, restricted stock and performance share units									1,101	955	846
Diluted weighted average common shares outstanding	77,597	77,523	77,320	76,894	76,806	76,880	76,674	76,699	77,333	76,758	77,972