Summary of Significant Accounting Policies (Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Accounting Policies [Abstract]
Net income	$ 109,242	$ 113,981
Shares used to compute basic earnings per common share (in shares)	149,468	153,310
Dilutive effect of stock options (in shares)	2,900	3,231
Shares used to compute diluted earnings per common share (in shares)	152,368	156,541
Basic earnings per common share (in USD per share)	$ 0.73	$ 0.74
Diluted earnings per common share (in USD per share)	$ 0.72	$ 0.73