Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	551	0	938	0
Net Income (Loss) Attributable to Parent [Abstract]
Net income attributable to common stockholders	$ 47,727	$ 47,448	$ 110,792	$ 161,418
After tax interest on convertible debt	13	13	35	37
Net income — diluted	$ 47,740	$ 47,461	$ 110,827	$ 161,455
Weighted average shares (denominator):
Weighted average shares — basic	(193,274)	(199,310)	(193,999)	(201,729)
Convertible debt	121	121	121	121
Weighted average shares — diluted	196,567	203,444	197,175	205,950
Net income attributable to common stockholders, basic	$ 0.25	$ 0.24	$ 0.57	$ 0.80
Net income attributable to common stockholders, diluted	$ 0.24	$ 0.23	$ 0.56	$ 0.78
Equity Option [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Stock options	3,154	4,013	3,049	4,100
Restricted Stock Units (RSUs) [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Stock options	18	0	6	0
Equity Option [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	551	0	936	0
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	2	0