Fair Value Measurement - Summary of Activity for Account Balances Whose Fair Value Measurements are Estimated Utilizing Level 3 Inputs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Redeemable Noncontrolling Interests [Roll Forward]
Redeemable Non-controlling Interests (Temporary Equity) Balance			$ 96,251	$ 133,000
Dividends: declared and paid - $0.60 per share			700
Repurchases of class A common shares: 10,302,935			1,081
Dividends paid to non-controlling interest			(9,896)	(21,928)
Redeemable Non-controlling Interests (Temporary Equity) Balance	$ 93,178	$ 119,460	93,178	119,460
Redeemable Non-controlling Interests [Member]
Redeemable Noncontrolling Interests [Roll Forward]
Redeemable Non-controlling Interests (Temporary Equity) Balance	95,111	124,763	96,251	133,000
Dividends: declared and paid - $0.60 per share	0	0	700	0
Repurchases of class A common shares: 10,302,935	0	0	1,081	0
Dividends paid to non-controlling interest	(3,228)	(5,863)	(9,896)	(21,928)
Net income attributable to non-controlling interests	1,295	560	5,042	8,388
Redeemable Non-controlling Interests (Temporary Equity) Balance	$ 93,178	$ 119,460	$ 93,178	$ 119,460