Earnings Per Share Level 4 (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net income attributable to common stockholders	$ 33,615	$ 37,076	$ 91,236	$ 85,101
After tax interest on convertible debt	13	13	25	26
Net income — diluted	$ 33,628	$ 37,089	$ 91,261	$ 85,127
Weighted average shares — basic	(211,821)	(215,898)	(211,602)	(218,015)
Stock options	4,004	2,887	3,880	2,922
Convertible debt	121	121	121	121
Weighted average shares — diluted	215,946	218,906	215,603	221,058
Net income attributable to common stockholders, basic	$ 0.16	$ 0.17	$ 0.43	$ 0.39
Net income attributable to common stockholders, diluted	$ 0.16	$ 0.17	$ 0.42	$ 0.39