Earnings per Share Basic and Diluted EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Numerator [Line items]
Net income	$ 56,785	$ 63,362	$ 132,203	$ 140,103
Denominators [Line Items]
Weighted average Class A common shares outstanding – Basic	57,266	56,819	57,160	56,673
Weighted average Class B common shares outstanding	793	828	793	915
Dilutive effect of employee stock-based awards	121	199	130	245
Weighted average shares - Diluted	58,180	57,846	58,083	57,833
Earnings per common share [Line Items]
Basic earnings per common share	$ 0.99	$ 1.12	$ 2.31	$ 2.47
Diluted earnings per common share	$ 0.98	$ 1.10	$ 2.28	$ 2.42