Summary of Significant Accounting Policies (Net Income Per Share) (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Weighted Average Number of Shares Outstanding, Basic	71,746	72,420	72,000
Incremental Weighted Average Shares Attributable to Dilutive Effect [Abstract]
Weighted Average Number of Shares Outstanding, Diluted	72,410	73,190	72,854
Employee Stock Option [Member]
Incremental Weighted Average Shares Attributable to Dilutive Effect [Abstract]
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	13	148	225
Restricted Stock Units (RSUs) [Member]
Incremental Weighted Average Shares Attributable to Dilutive Effect [Abstract]
Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements	651	622	629