Business and Basis of Presentation - Additional Information (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($) business	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue recognized previously attributable to deferred revenues	$ 675,200,000	$ 642,000,000.0	$ 1,312,300,000	$ 1,164,200,000
Acquisition and integration charges	1,742,000	17,114,000	4,156,000	96,342,000
Business exit costs				51,400,000
Deferred consideration from pre-2018 acquisitions			2,295,000	$ 15,855,000
Number of businesses sold | business				3
Disposal group, revenue		8,600,000		$ 97,000,000.0
Disposal group, pre-tax income		4,900,000		60,100,000
Cash received from divestitures			0	520,709,000
Gain (loss) from divested operations	0	13,040,000	(2,075,000)	38,500,000
Unrealized appreciation			9,120,000	0
Cash and cash equivalents and restricted cash, beginning of period	306,727,000	$ 213,292,000	306,727,000	$ 213,292,000		$ 158,663,000	$ 567,058,000
Cash and cash equivalents	306,727,000		306,727,000			156,368,000
Restricted cash						2,300,000
Operating leases - right-of-use assets	652,273,000		652,273,000		$ 651,900,000
Lease liabilities	856,732,000		856,732,000		851,300,000
Total Assets	6,737,344,000		6,737,344,000			6,201,474,000
Total Liabilities	$ 5,817,687,000		$ 5,817,687,000			$ 5,350,717,000
Renewal term	5 years		5 years
Option to terminate, term			1 year
ASU 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total Assets					638,700,000
Total Liabilities					$ 638,700,000
Other income (expense)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Unrealized appreciation	$ 9,100,000		$ 9,100,000
Prepaid expenses and other current assets
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Minority equity investment fair value	$ 14,100,000		$ 14,100,000