Acquisitions and Divestitures - Schedule of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	11 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Nov. 02, 2017
Business Acquisition [Line Items]
Goodwill	$ 2,097,990	$ 2,153,988
Alliance Automotive Group [Member]
Business Acquisition [Line Items]
Trade accounts receivable	386,000		$ 380,000
Merchandise inventories	378,000		374,000
Prepaid expenses and other current assets	226,000		213,000
Intangible assets	813,000		727,000
Deferred tax assets	6,000		4,000
Property and equipment	92,000		93,000
Other assets	14,000		25,000
Total identifiable assets acquired	1,915,000		1,816,000
Current liabilities	(820,000)		(768,000)
Long-term debt	(769,000)		(769,000)
Pension and other post-retirement benefit liabilities	(14,000)		(14,000)
Deferred tax liabilities	(176,000)		(151,000)
Other long-term liabilities	(34,000)		(32,000)
Total liabilities assumed	(1,813,000)		(1,734,000)
Net identifiable assets acquired	102,000		82,000
Noncontrolling interests in subsidiaries	(38,000)		(38,000)
Goodwill	1,003,000		1,036,000
Net assets acquired	1,067,000		$ 1,080,000
Measurement Period Adjustments
Trade accounts receivable	6,000
Merchandise inventories	4,000
Prepaid expenses and other current assets	13,000
Intangible assets	86,000
Deferred tax assets	2,000
Property and equipment	(1,000)
Other assets	(11,000)
Total identifiable assets acquired	99,000
Current liabilities	(52,000)
Long-term debt	0
Pension and other post-retirement benefit liabilities	0
Deferred tax liabilities	(25,000)
Other long-term liabilities	(2,000)
Total liabilities assumed	(79,000)
Net identifiable assets acquired	20,000
Noncontrolling interests in subsidiaries	0
Goodwill	(33,000)
Net assets acquired	$ (13,000)