Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,799,000,000	1,000,000	2,362,000,000	1,034,000,000
Net Income (Loss) Attributable to Parent [Abstract]
Net income attributable to common stockholders	$ 15,620	$ 52,595	$ 63,065	$ 113,970
After tax interest on convertible debt	10	12	22	25
Net income — diluted	$ 15,630	$ 52,607	$ 63,087	$ 113,995
Weighted average shares (denominator):
Weighted average shares — basic	(193,806,000)	(202,466,000)	(194,366,000)	(202,966,000)
Convertible debt	121,000	121,000	121,000	121,000
Weighted average shares — diluted	196,718,000	206,746,000	197,463,000	207,221,000
Net income attributable to common stockholders, basic	$ 0.08	$ 0.26	$ 0.32	$ 0.56
Net income attributable to common stockholders, diluted	$ 0.08	$ 0.25	$ 0.32	$ 0.55
Equity Option [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Stock options	2,788,000	4,159,000	2,975,000	4,134,000
Restricted Stock Units (RSUs) [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Stock options	3,000	0	1,000	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	1,799,000,000	1,000,000	2,338,000,000	1,034,000,000
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	24,000,000	0