Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Numerator:
Net income from continuing operations	$ 47,105	$ 45,437	$ 139,137	$ 144,322
Income from discontinued operations, net of tax	29,848	11,921	39,543	27,070
Net income (numerator for diluted EPS)	76,953	57,358	178,680	171,392
Less: Preference stock dividend	8	9	24	28
Income attributable to common stockholders (numerator for basic EPS)	$ 76,945	$ 57,349	$ 178,656	$ 171,364
Denominator:
Weighted-average shares used in basic EPS (in shares)	187,470	186,497	187,167	186,257
Effect of dilutive shares (in shares)	945	1,260	1,023	943
Weighted-average shares used in diluted EPS (in shares)	188,415	187,757	188,190	187,200
Basic earnings per share(1):
Continuing operations (in dollars per share)	$ 0.25	$ 0.24	$ 0.74	$ 0.77
Discontinued operations (in dollars per share)	0.16	0.06	0.21	0.15
Net Income (in dollars per share)	0.41	0.31	0.95	0.92
Diluted earnings per share(1):
Continuing operations (in dollars per share)	0.25	0.24	0.74	0.77
Discontinued operations (in dollars per share)	0.16	0.06	0.21	0.14
Net Income (in dollars per share)	$ 0.41	$ 0.31	$ 0.95	$ 0.92
Anti-dilutive shares not used in calculating diluted weighted-average shares (in shares)	12,195	9,927	12,097	10,211