Consolidated Statements of Changes In Equity - USD ($) $ in Thousands	Total	Common Shares $1 Par Value [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Subtotal [Member]	Noncontrolling Interest [Member]
Beginning Balance at Dec. 31, 2015	$ 10,465,890	$ 362,617	$ 4,986,819	$ 438,793	$ 4,612,982	$ 10,401,211	$ 64,679
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(167,403)				(165,591)	(165,591)	(1,812)
Other comprehensive income, net of taxes	(25,521)			(25,521)		(25,521)
Contributions from noncontrolling interests	116,180					0	116,180
Distributions to noncontrolling interests	(834)					0	(834)
Deconsolidation of asset management entities	(385)					0	(385)
Change in interest in consolidated subsidiary	0		(369)			(369)	369
Share-based compensation expense	16,055		16,055			16,055
Change in fair value of redeemable noncontrolling interests	(31,631)		(31,631)			(31,631)
Purchase of common shares for treasury	(59,227)	(3,565)	(55,662)			(59,227)
Dividends ($.125 per common share)	(47,130)				(47,130)	(47,130)
Other	(1,436)	1,353	(2,632)			(1,279)	(157)
Ending Balance at Jun. 30, 2016	10,264,558	360,405	4,912,580	413,272	4,400,261	10,086,518	178,040
Beginning Balance at Dec. 31, 2015	10,465,890	362,617	4,986,819	438,793	4,612,982	10,401,211	64,679
Ending Balance at Jun. 30, 2017	10,680,165	358,645	4,843,966	350,442	4,938,254	10,491,307	188,858
Beginning Balance at Dec. 31, 2016	10,303,649	359,425	4,812,587	310,697	4,645,391	10,128,100	175,549
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	337,632				339,601	339,601	(1,969)
Other comprehensive income, net of taxes	39,745			39,745		39,745
Contributions from noncontrolling interests	24,669					0	24,669
Distributions to noncontrolling interests	(9,347)					0	(9,347)
Change in interest in consolidated subsidiary	0		44			44	(44)
Share-based compensation expense	20,375		20,375			20,375
Change in fair value of redeemable noncontrolling interests	39,965		39,965			39,965
Exercise of options to purchase common shares	462	20	442			462
Purchase of common shares for treasury	(34,072)	(1,359)	(32,713)			(34,072)
Dividends ($.125 per common share)	(46,738)				(46,738)	(46,738)
Other	3,825	559	3,266			3,825
Ending Balance at Jun. 30, 2017	$ 10,680,165	$ 358,645	$ 4,843,966	$ 350,442	$ 4,938,254	$ 10,491,307	$ 188,858