Earnings Per Share Level 4 (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2015		Sep. 30, 2015		Jun. 30, 2015		Mar. 31, 2015		Dec. 31, 2014		Sep. 30, 2014		Jun. 30, 2014		Mar. 31, 2014		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net Income (Loss) Attributable to Parent [Abstract]
Income from continuing operations attributable to common stockholders, basic																	$ 234,162	$ 170,283	$ 146,926
Income from continuing operations — diluted																	234,212	170,334	146,977
Net income attributable to common stockholders	$ 72,354		$ 47,448		$ 52,595		$ 61,375		$ 87,794		$ 17,651		$ 25,922		$ 41,102		233,772	172,469	147,332
After tax interest on convertible debt																	50	51	51
Income from discontinued operations, net	$ 0		$ 0		$ (390)		$ 0		$ 1,340		$ 884		$ (178)		$ 140		(390)	2,186	406
Net income — diluted																	$ 233,822	$ 172,520	$ 147,383
Weighted average shares (denominator):
Weighted average shares — basic																	200,356	210,741	211,811
Stock options																	3,973	3,338	4,082
Convertible debt																	121	121	121
Weighted average shares — diluted																	204,450	214,200	216,014
Net income attributable to common stockholders, basic	$ 0.37	[1]	$ 0.24	[1]	$ 0.26	[1]	$ 0.30	[1]	$ 0.42	[1]	$ 0.08	[1]	$ 0.12	[1]	$ 0.19	[1]	$ 1.17	$ 0.82	$ 0.70
Net income attributable to common stockholders, diluted	$ 0.36	[1]	$ 0.23	[1]	$ 0.25	[1]	$ 0.30	[1]	$ 0.42	[1]	$ 0.08	[1]	$ 0.12	[1]	$ 0.19	[1]	1.14	0.81	0.68
Income from continuing operations attributable to common stockholders, per share, basic																		0.81	0.70
Income from continuing operations attributable to common stockholders, per share, diluted																		0.80	0.68
Income from discontinued operations per share, basic																	0.00	0.01	0
Income from discontinued operations per share, diluted																	$ 0.00	$ 0.01	$ 0
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount																	3	1,500	1,200

[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.