Earnings Per Share Level 4 (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net income attributable to common stockholders	$ 48,025	$ 38,764
After tax interest on convertible debt	13	13
Net income — diluted	$ 48,038	$ 38,777
Weighted average shares — basic	(220,132)	(239,772)
Stock options	2,959	2,159
Convertible debt	121	121
Weighted average shares — diluted	223,212	242,052
Net income attributable to common stockholders, basic	$ 0.22	$ 0.16
Net income attributable to common stockholders, diluted	$ 0.22	$ 0.16