Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net income	$ 79,955	$ 92,512	$ 153,934	$ 147,699
Weighted average number of common shares outstanding - basic (in shares)	217,089	216,342	216,900	216,309
Effect of dilutive securities:
Weighted average number of common shares outstanding - diluted (in shares)	217,905	216,515	217,555	216,753
Net income per share – basic (In dollars per share)	$ 0.37	$ 0.43	$ 0.71	$ 0.68
Net income per share – diluted (In dollars per share)	$ 0.37	$ 0.43	$ 0.71	$ 0.68
Restricted stock units
Effect of dilutive securities:
Dilutive securities (in shares)	476	2	327	90
Performance share units
Effect of dilutive securities:
Dilutive securities (in shares)	315	0	286	108
Stock options
Effect of dilutive securities:
Dilutive securities (in shares)	25	171	42	246