Changes in Equity (Rollforward) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Balances	$ 3,775,989	$ 3,195,068
Dividends declared	(53,504)	(44,269)
Share repurchases	(84,308)	(69,269)
Equity-based compensation	6,695	5,132
Net income	204,827	225,475
Other comprehensive loss, net of tax	(171)
Comprehensive and net income (loss)	204,656	225,475
Balances	3,849,528	3,312,137
Common Stock
Balances	645	644
Balances	645	644
Treasury Stock
Balances	(1,184,243)	(665,297)
Share repurchases	(84,308)	(69,269)
Equity-based compensation	6,714	3,866
Balances	(1,261,837)	(730,700)
Additional Paid-In Capital
Balances	1,160,048	1,141,534
Equity-based compensation	91	1,337
Balances	1,160,139	1,142,871
Retained Earnings
Balances	3,958,320	2,874,693
Dividends declared	(53,504)	(44,269)
Equity-based compensation	(110)	(71)
Net income	204,328
Comprehensive and net income (loss)		227,551
Balances	4,109,034	3,057,904
AOCI Attributable to Parent [Member]
Balances	301
Other comprehensive loss, net of tax	(171)
Balances	130
Noncontrolling Interests
Balances	(159,082)	(156,506)
Net income	499
Comprehensive and net income (loss)		(2,076)
Balances	(158,583)	(158,582)
Redeemable Noncontrolling Interest
Balances	111,240	111,240
Noncontrolling investors of USS	28,690
Balances	$ 139,930	$ 111,240

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income. Excludes changes in equity resulting from investments by owners and distributions to owners.

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