Earnings Per Share Level 4 (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net income attributable to common stockholders	$ 41,062	$ 35,496	$ 126,163	$ 100,353
After tax interest on convertible debt	13	13	38	38
Net income — diluted	$ 41,075	$ 35,509	$ 126,201	$ 100,391
Weighted average shares — basic	(214,914)	(232,917)	(216,974)	(237,037)
Stock options	3,425	2,475	3,211	2,370
Convertible debt	121	121	121	121
Weighted average shares — diluted	218,460	235,513	220,306	239,528
Net income attributable to common stockholders, basic	$ 0.19	$ 0.15	$ 0.58	$ 0.42
Net income attributable to common stockholders, diluted	$ 0.19	$ 0.15	$ 0.57	$ 0.42