Earnings Per Share Level 4 (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2017		Sep. 30, 2017		Jun. 30, 2017		Mar. 31, 2017		Dec. 31, 2016		Sep. 30, 2016		Jun. 30, 2016		Mar. 31, 2016		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net Income (Loss) Attributable to Parent [Abstract]
Income from continuing operations attributable to common stockholders, basic																	$ 546,663	$ 177,038	$ 234,162
Income from continuing operations — diluted																	546,715	177,081	234,212
Net income attributable to common stockholders	$ 247,316		$ 56,164		$ 68,481		$ 174,702		$ 66,246		$ 47,727		$ 15,620		$ 47,445		546,663	177,038	233,772
After tax interest on convertible debt																	52	43	50
Income from discontinued operations, net																	0	0	(390)
Net income — diluted																	$ 546,715	$ 177,081	$ 233,822
Weighted average shares (denominator):
Weighted average shares — basic																	187,630	193,086	200,356
Convertible debt																	121	121	121
Weighted average shares — diluted																	192,246	196,042	204,450
Net income attributable to common stockholders, basic	$ 1.32	[1]	$ 0.30	[1]	$ 0.37	[1]	$ 0.93	[1]	$ 0.35	[1]	$ 0.25	[1]	$ 0.08	[1]	$ 0.24	[1]	$ 2.91	$ 0.92	$ 1.17
Net income attributable to common stockholders, diluted	$ 1.29	[1]	$ 0.29	[1]	$ 0.36	[1]	$ 0.91	[1]	$ 0.34	[1]	$ 0.24	[1]	$ 0.08	[1]	$ 0.24	[1]	$ 2.84	0.90	1.14
Income from continuing operations attributable to common stockholders, per share, basic																		0.92	1.17
Income from continuing operations attributable to common stockholders, per share, diluted																		$ 0.90	$ 1.14
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount																	911,000	982,000	3,000
Stock Options [Member]
Weighted average shares (denominator):
Share based compensation																	4,396	2,823	3,973
Restricted Stock Units (RSUs) [Member]
Weighted average shares (denominator):
Share based compensation																	99	12	0

[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.