Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net income	$ 73,979	$ 55,187
Weighted average number of common shares outstanding - basic (in shares)	216,709	216,276
Effect of dilutive securities:
Weighted average number of common shares outstanding - diluted (in shares)	217,202	216,989
Net income per share – basic (In dollars per share)	$ 0.34	$ 0.26
Net income per share – diluted (In dollars per share)	$ 0.34	$ 0.25
Restricted stock units
Effect of dilutive securities:
Dilutive securities (in shares)	179	177
Performance share units
Effect of dilutive securities:
Dilutive securities (in shares)	256	216
Stock options
Effect of dilutive securities:
Dilutive securities (in shares)	58	320

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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