Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Net Income (Loss) Attributable to Parent [Abstract]
Net income attributable to common stockholders	$ 81,988	$ 174,702
After tax interest on convertible debt	15	12
Net income — diluted	$ 82,003	$ 174,714
Weighted average shares (denominator):
Weighted average shares — basic	(185,130)	(188,260)
Convertible debt	121	121
Weighted average shares — diluted	189,923	192,867
Net income attributable to common stockholders, basic	$ 0.44	$ 0.93
Net income attributable to common stockholders, diluted	$ 0.43	$ 0.91
Equity Option [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Stock options	4,522	4,425
Restricted Stock Units (RSUs) [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Stock options	150	61
Equity Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	577	898