Income Taxes - Components of Provision and Current Receivable (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Tax Cuts and Jobs Act of 2017
Corporate tax rate (as a percent)		21.00%	35.00%	35.00%
Additional income tax expense from on-time revaluation of certain tax-related assets	$ 47,600
Current:
Federal		$ 69,477	$ 101,162	$ 118,080
State and local		27,909	24,595	20,253
Total current		97,386	125,757	138,333
Deferred:
Federal		(2,043)	58,732	2,211
State and local		(1,559)	184	1,107
Total deferred		(3,602)	58,916	3,318
Total provision for income taxes		93,784	184,673	$ 141,651
Receivables
Current income tax receivable due from various jurisdictions	$ 53,200	$ 25,300	$ 53,200