Segment Reporting - Summary of Geographic Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 1,320,106	$ 1,125,912	$ 2,592,351	$ 2,222,877
Percent of revenues	1.000	1.000	1.000	1.000
Total assets	$ 33,148,697		$ 33,148,697		$ 30,342,072	[1]
Percent of assets	1.000		1.000		1.000
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 1,092,376	$ 895,734	$ 2,136,042	$ 1,759,523
Percent of revenues	0.828	0.795	0.824	0.791
Total assets	$ 27,496,270		$ 27,496,270		$ 24,884,292
Percent of assets	0.829		0.829		0.820
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 112,647	$ 112,031	$ 225,065	$ 228,556
Percent of revenues	0.085	0.100	0.087	0.103
Total assets	$ 3,173,654		$ 3,173,654		$ 3,078,994
Percent of assets	0.096		0.096		0.101
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 115,083	$ 118,147	$ 231,244	$ 234,798
Percent of revenues	0.087	0.105	0.089	0.106
Total assets	$ 2,478,773		$ 2,478,773		$ 2,378,786
Percent of assets	0.075		0.075		0.079

[1] The consolidated balance sheet at December 31, 2018 has been derived from the audited financial statements at that date but does not include all of the information and footnotes required by U.S. generally accepted accounting principles for complete financial statements.