Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Treasury Stock.	Retained Earnings	Redeemable Noncontrolling Interest	Total
Changes in Total Equity
Cumulative effect adjustment from adoption of ASU 2014-09 (Note 2) | Adjustments for New Accounting Pronouncement | ASU 2014-09					$ (4,445)		$ (4,445)
Balance (Previously reported) at Dec. 31, 2017						$ 115,689
Changes in Redeemable Noncontrolling Interests
Net income						1,261
Adjustments to redemption value of redeemable noncontrolling interest						12,828
Subsidiary repurchase of noncontrolling interests						(3,778)
Balance (Previously reported) at Dec. 31, 2017	$ 20,277	$ 162,806	$ (36,148)	$ (909,960)	3,004,018		$ 2,240,993
Balance (in shares) (Previously reported) at Dec. 31, 2017	202,765
Balance (in shares) at Dec. 31, 2017							202,765,000
Changes in Total Equity
Reclassification from adoption of ASU 2018-02 (Notes 1 and 4			2,329		(2,329)
Net income					440,236		$ 440,236
Other comprehensive loss			(16,267)				(16,267)
Common stock issued from treasury shares for exercise of stock options		7,075		23,943			31,018
Common stock unissued due to forfeiture of nonvested awards		658		(658)
Common stock issued from treasury shares for nonvested awards		(13,163)		13,163
Common stock issued from treasury for dividend equivalents		925		9			934
Share-based compensation		32,682					32,682
Cash dividends declared ($0.13 per share)					(71,698)		(71,698)
Purchase of treasury shares				(443)			(443)
Adjustments to redemption value of redeemable noncontrolling interest		(12,828)					(12,828)
Subsidiary repurchase of noncontrolling interests						$ (126,000)
Balance at Sep. 30, 2018	$ 20,277	$ 178,155	$ (50,086)	$ (873,946)	$ 3,365,782		$ 2,640,182
Balance (in shares) at Sep. 30, 2018	202,765						202,765,000