Earnings Per Share Level 4 (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2013		Sep. 30, 2013		Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Net Income (Loss) Attributable to Parent [Abstract]
Net income attributable to common stockholders	$ 25,833		$ 26,779		$ 33,615		$ 57,620		$ 26,383		$ 41,062		$ 37,076		$ 48,025		$ 143,848	$ 152,546	$ 144,903
After tax interest on convertible debt																	51	51	51
Net income — diluted																	$ 143,899	$ 152,597	$ 144,954
Weighted average shares (denominator):
Weighted average shares — basic																	(211,811)	(215,712)	(234,242)
Stock options																	4,082	3,233	2,306
Convertible debt																	121	121	121
Weighted average shares — diluted																	216,014	219,066	236,669
Net income attributable to common stockholders, basic	$ 0.12	[1]	$ 0.13	[1]	$ 0.16	[1]	$ 0.27	[1]	$ 0.12	[1]	$ 0.19	[1]	$ 0.17	[1]	$ 0.22	[1]	$ 0.68	$ 0.71	$ 0.62
Net income attributable to common stockholders, diluted	$ 0.12	[1]	$ 0.12	[1]	$ 0.16	[1]	$ 0.27	[1]	$ 0.12	[1]	$ 0.19	[1]	$ 0.17	[1]	$ 0.22	[1]	$ 0.67	$ 0.70	$ 0.61

[1] Net income per share is computed independently for each of the quarters presented. Therefore, the sum of the quarters’ net income per share may not equal the total computed for the year.