Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Net Income (Loss) Attributable to Parent [Abstract]
Net income attributable to common stockholders	$ 25,922	$ 33,615	$ 67,024	$ 91,236
After tax interest on convertible debt	13	13	25	25
Net income — diluted	$ 25,935	$ 33,628	$ 67,049	$ 91,261
Weighted average shares (denominator):
Weighted average shares — basic	(212,390)	(211,821)	(212,613)	(211,602)
Stock options	3,478	4,004	3,859	3,880
Convertible debt	121	121	121	121
Weighted average shares — diluted	215,989	215,946	216,593	215,603
Net income attributable to common stockholders, basic	$ 0.12	$ 0.16	$ 0.32	$ 0.43
Net income attributable to common stockholders, diluted	$ 0.12	$ 0.16	$ 0.31	$ 0.42