Earnings per Share (EPS) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Numerator:
(Loss) income from continuing operations									$ (191,659)		$ 40,149		$ 181,705
Income from discontinued operations, net of tax	$ 2,467	$ 616	$ (3,032)	$ 10,064	$ 168,659	$ (8,470)	$ (5,613)	$ (116)	10,115		154,460		60,106
Net (loss) income	$ 18,879	$ 11,389	$ (3,329)	$ (208,483)	$ 176,696	$ (3,125)	$ 23,697	$ (2,659)	(181,544)		194,609		241,811
Less: Preference stock dividend									0		8		32
(Loss) income attributable to common stockholders (numerator for basic EPS)									$ (181,544)		$ 194,601		$ 241,779
Denominator:
Weighted-average shares used in basic EPS (in shares)									171,519,000		176,251,000		187,277,000
Dilutive effect of common stock equivalents (shares)									0		1,198,000		1,105,000
Weighted-average shares used in diluted EPS (in shares)									171,519,000		177,449,000		188,382,000
Basic earnings per share
Continuing operations (in dollars per share)	$ 0.10	$ 0.06	$ 0	$ (1.28)	$ 0.05	$ 0.03	$ 0.17	$ (0.01)	$ (1.12)	[1]	$ 0.23	[1]	$ 0.97	[1]
Discontinued operations (in dollars per share)	0.01	0	(0.02)	0.06	0.99	(0.05)	(0.03)	0	0.06	[1]	0.88	[1]	0.32	[1]
Net income (in dollars per share)	0.11	0.07	(0.02)	(1.22)	1.04	(0.02)	0.13	(0.01)	(1.06)	[1]	1.10	[1]	1.29	[1]
Diluted earnings per share
Continuing operations (in dollars per share)	0.09	0.06	0	(1.28)	0.05	0.03	0.16	(0.01)	(1.12)	[1]	0.23	[1]	0.96	[1]
Discontinued operations (in dollars per share)	0.01	0	(0.02)	0.06	0.98	(0.05)	(0.03)	0	0.06	[1]	0.87	[1]	0.32	[1]
Net income (in dollars per share)	$ 0.11	$ 0.07	$ (0.02)	$ (1.22)	$ 1.03	$ (0.02)	$ 0.13	$ (0.01)	$ (1.06)	[1]	$ 1.10	[1]	$ 1.28	[1]
Anti-dilutive options excluded from diluted earnings per share (in shares)									11,626,000		15,751,000		12,089,000
Dilutive effect of common stock equivalents (shares)									2,483,000

[1] The sum of the earnings per share amounts may not equal the totals due to rounding.