Earnings Per Share (Details) $ / shares in Units, shares in Thousands, $ in Thousands		1 Months Ended	3 Months Ended		6 Months Ended
	Feb. 01, 2017 $ / shares	Jan. 31, 2017 $ / shares	Jun. 30, 2017 USD ($) $ / shares shares	Jun. 30, 2016 USD ($) $ / shares shares	Jun. 30, 2017 USD ($) $ / shares shares	Jun. 30, 2016 USD ($) $ / shares shares
Numerator:
Income from continuing operations | $			$ 108,829	$ 106,289	$ 179,154	$ 179,543
Income (loss) from discontinued operations, net of income taxes | $			0	14,609	(42,704)	24,818
Net income | $			$ 108,829	$ 120,898	$ 136,450	$ 204,361
Denominator:
Denominator for basic net earnings per share - weighted-average shares outstanding (shares) | shares			151,212	154,998	152,247	154,485
Effect of dilutive employee stock awards (shares) | shares			2,180	1,668	2,815	1,773
Effect of dilutive Convertible Notes (shares) | shares			2,644	0	2,177	0
Denominator for net diluted earnings per share - weighted-average shares outstanding (shares) | shares			156,036	156,666	157,239	156,258
Income from continuing operations, basic (in dollars per share)			$ 0.72	$ 0.69	$ 1.18	$ 1.16
Income (loss) from discontinued operations, basic (in dollars per share)			0.00	0.09	(0.28)	0.16
Basic earnings per share (in dollars per share)			0.72	0.78	0.90	1.32
Income from continuing operations, diluted (in dollars per share)			0.70	0.68	1.14	1.15
Income (loss) from discontinued operations, diluted (in dollars per share)			0.00	0.09	(0.27)	0.16
Diluted earnings per share (in dollars per share)			$ 0.70	$ 0.77	$ 0.87	$ 1.31
Anti-dilutive weighted-average shares from stock awards (shares) | shares			274	296	977	574
Senior Notes Due 2019 [Member]
Denominator:
Convertible debt, conversion price (in dollars per share)	$ 71.91	$ 90
Convertible debt, conversion ratio	0.0139061	0.011111
GetGo, Inc. [Member]
Denominator:
Convertible debt, conversion price (in dollars per share)	$ 71.91
Convertible debt, conversion ratio	0.0139061