Earnings Per Share Level 4 (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net income attributable to common stockholders	$ 57,620	$ 48,025
After tax interest on convertible debt	13	13
Net income — diluted	$ 57,633	$ 48,038
Weighted average shares — basic	(211,380)	(220,132)
Stock options	3,707	2,959
Convertible debt	121	121
Weighted average shares — diluted	215,208	223,212
Net income attributable to common stockholders, basic	$ 0.27	$ 0.22
Net income attributable to common stockholders, diluted	$ 0.27	$ 0.22