Summary of Significant Accounting Policies - Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Income tax (benefit), net of refunds	$ 21,173	$ 2,186	$ 9,956
Interest, net of amounts capitalized	208,479	189,288	184,462
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Accrued capital expenditures	132,620	130,404	114,855
Dividends declared but not paid	82,675	77,667	72,926
Sale of 4CA 7% interest in Four Corners	$ 68,907	$ 0	$ 0