Consolidated Statements of Equity (Unaudited) - USD ($)	Total	Additional Paid-In Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive (Loss) Income	Noncontrolling Interest	Common stock Class A	Common Stock Class B
Balance at Dec. 31, 2013	$ 1,926,119,000	$ 1,095,748,000	$ 570,793,000	$ (15,978,000)	$ (76,582,000)	$ 285,913,000	$ 59,500,000	$ 6,725,000
Balance, Shares at Dec. 31, 2013				942,000			178,499,000	20,173,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss, net of $14,812 and $17,095 attributable to redeemable noncontrolling interest	(3,925,000)		(7,595,000)			3,670,000
Other comprehensive income, net of tax	17,791,000				17,736,000	55,000
Purchase of treasury stock	(4,009,000)			$ (4,009,000)
Purchase of treasury stock, Shares				215,000
Conversion of Class B to Class A shares	0						$ 322,000	$ (322,000)
Conversion of Class B to Class A shares, Shares							964,000	(964,000)
Restricted stock vested	0	(240,000)					$ 240,000
Restricted stock vested, Shares							723,000
Exercise of stock options	789,000	(276,000)		$ 1,065,000
Exercise of stock options, Shares				(62,000)
Stock-based compensation	19,673,000	19,673,000
Write-off of deferred tax asset related to expired stock options	(419,000)	(419,000)
Exchange of Class A Common Units for Class A shares	0	34,134,000				(34,358,000)	$ 224,000
Exchange of Class A Common Units for Class A shares, shares							673,000
Redeemable noncontrolling interest adjustment	(28,390,000)	(28,390,000)
Acquisition of partners' noncontrolling interest in consolidated subsidiaries	(99,863,000)	(32,505,000)				(67,358,000)
Contributions from noncontrolling interests	175,274,000					175,274,000
Distributions to noncontrolling interests	(14,634,000)					(14,634,000)
Adjustment due to change in ownership of consolidated subsidiaries	(3,935,000)	78,103,000				(82,038,000)
Change in control of equity method subsidiary	168,252,000					168,252,000
Balance at Dec. 31, 2014	2,152,723,000	1,165,828,000	563,198,000	$ (18,922,000)	(58,846,000)	434,776,000	$ 60,286,000	$ 6,403,000
Balance, Shares at Dec. 31, 2014				1,095,000			180,859,000	19,209,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss, net of $14,812 and $17,095 attributable to redeemable noncontrolling interest	(42,226,000)		(52,672,000)			10,446,000
Other comprehensive income, net of tax	8,899,000				8,887,000	12,000
Issuance of Class A shares in equity offering	806,500,000	794,042,000					$ 12,458,000
Issuance of Class A shares in equity offering, shares							37,375,000
Purchase of treasury stock	$ (5,412,000)			$ (5,412,000)
Purchase of treasury stock, Shares	216,700			217,000
Conversion of Class B to Class A shares	$ 0						$ 128,000	$ (128,000)
Conversion of Class B to Class A shares, Shares							385,000	(385,000)
Proceeds and Class A shares received from termination of Convertible Senior Notes hedge,	17,818,000	24,321,000		$ (6,503,000)
Proceeds and Class A shares received from termination of Convertible Senior Notes hedge, shares				258,000
Issuance of Class A shares in exchange for Convertible Senior Notes	410,580,000	403,924,000					$ 6,656,000
Issuance of Class A shares in exchange for Convertible Senior Notes, Shares							19,967,000
Restricted stock vested	0	(246,000)					$ 246,000
Restricted stock vested, Shares							736,000
Exercise of stock options	955,000	(235,000)		$ 1,190,000
Exercise of stock options, Shares				(61,000)
Stock-based compensation	21,536,000	21,536,000
Write-off of deferred tax asset related to expired stock options	(1,536,000)	(1,536,000)
Exchange of Class A Common Units for Class A shares	0	52,319,000				(52,663,000)	$ 344,000
Exchange of Class A Common Units for Class A shares, shares							1,032,000
Acquisition of partners' noncontrolling interest in consolidated subsidiaries	(308,000)	(299,000)				(9,000)
Contributions from noncontrolling interests	77,369,000					77,369,000
Distributions to noncontrolling interests	(28,588,000)					(28,588,000)
Adjustment due to change in ownership of consolidated subsidiaries	(48,000)	479,000				(527,000)
Balance at Sep. 30, 2015	$ 3,418,262,000	$ 2,460,133,000	$ 510,526,000	$ (29,647,000)	$ (49,959,000)	$ 440,816,000	$ 80,118,000	$ 6,275,000
Balance, Shares at Sep. 30, 2015				1,509,000			240,354,000	18,824,000