Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Net Income (Loss) Attributable to Parent [Abstract]
Net income attributable to common stockholders	$ 70,792	$ 68,935	$ 222,444	$ 254,162
After tax interest on convertible debt	0	15	0	45
Net income — diluted	$ 70,792	$ 68,950	$ 222,444	$ 254,207
Weighted average shares (denominator):
Weighted average shares — basic	(182,551)	(180,858)	(182,218)	(182,859)
Convertible debt	0	121	0	121
Weighted average shares — diluted	185,843	185,460	185,635	187,517
Net income attributable to common stockholders, basic	$ 0.39	$ 0.38	$ 1.22	$ 1.39
Net income attributable to common stockholders, diluted	$ 0.38	$ 0.37	$ 1.20	$ 1.36
Equity Option [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Stock options	3,225	4,284	3,370	4,364
Restricted Stock Units (RSUs) [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Stock options	67	197	47	173
Equity Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	785	831	641	980
Restricted Stock Units (RSUs) [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	0	0	58	0