Basis of Presentation (Earnings per share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator:
Net income	$ 348,620	$ 241,041	$ 552,331	$ 407,798
Less: earnings distributed to participating securities	(265)	(305)	(538)	(613)
Less: undistributed earnings allocated to participating securities	(2,602)	(2,089)	(4,358)	(3,588)
Numerator for basic earnings per share	345,753	238,647	547,435	403,597
Add back: undistributed earnings allocated to participating securities	2,602	2,089	4,358	3,588
Less: undistributed earnings reallocated to participating securities	(2,595)	(2,082)	(4,342)	(3,576)
Numerator for diluted earnings per share	$ 345,760	$ 238,654	$ 547,451	$ 403,609
Denominator:
Basic shares outstanding (shares)	268,324	276,652	269,167	277,142
Effect of dilutive securities (shares)	701	932	960	967
Diluted shares outstanding (shares)	269,025	277,584	270,127	278,109
Earnings per share:
Basic earnings (usd per share)	$ 1.29	$ 0.86	$ 2.03	$ 1.46
Diluted earnings (usd per share)	$ 1.29	$ 0.86	$ 2.03	$ 1.45