Basis and Summary of Significant Accounting Policies - Calculation of Dilutive Stock Awards (Details) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Accounting Policies [Abstract]
Weighted Average Shares Outstanding (in shares)	70,686	72,761	71,001	72,697
Dilutive Effect of Share-Based Awards (in shares)	1,011	518	1,039	551
Weighted Average Shares Outstanding Assuming Dilution (in shares)	71,697	73,279	72,040	73,248
Anti-dilutive securities excluded from the computation of earnings per share assuming dilution (in shares)	1	1,265	265	1,057