Accounting Standards Adopted and Newly Issued Accounting Standards Not Yet Adopted - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Jan. 01, 2019	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease obligations		$ 446,800		$ 446,800
Operating lease right-of-use assets		378,520		378,520
Adoption of ASC 842 (Note 3)	$ (5,030)
Income tax provision		$ 7,677	$ 11,883	$ 17,166	$ 17,521
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of ASC 842 (Note 3)	(5,030)
Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease obligations	453,000
Operating lease right-of-use assets	395,600
Income tax provision	(1,700)
Derecognition of certain liabilities and assets	(50,700)
Accrued rent	(43,300)
Accounting Standards Update 2016-02 | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Adoption of ASC 842 (Note 3)	$ 5,000