CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) shares in Millions, $ in Millions	Common Stock	Retained Earnings	Accumulated Other Comprehensive Loss	Nonredeemable Noncontrolling Interest	Total
Balance at Dec. 31, 2012	$ 1.9	$ 1,415.4	$ 0.6	$ 17.2	$ 1,435.1
Balance (in shares) at Dec. 31, 2012	187.5
Increase (Decrease) in Stockholders' Equity
Net income		114.7		1.1	115.8
Other comprehensive loss			(1.7)		(1.7)
Amortization of stock-based compensation		22.2		2.1	24.3
Issuance and forfeitures of restricted stock awards, net (in shares)	3.2
Stock option exercises and employee stock purchases		8.0			8.0
Stock option exercises and employee stock purchases (in shares)	1.4
Convertible senior notes issuance		14.7			14.7
Extinguishment of convertible senior notes		(2.0)			(2.0)
Convertible senior note hedge issuance		(16.1)			(16.1)
Stock warrants issuance		10.5			10.5
Changes in noncontrolling interests in consolidated investment products				(3.6)	(3.6)
Distributions to noncontrolling interests				(1.6)	(1.6)
Change in fair value of redeemable noncontrolling interests		1.8			1.8
Vesting of nonredeemable noncontrolling interests				(1.2)	(1.2)
Purchase of noncontrolling interests				(0.3)	(0.3)
Repurchase of common stock		(33.4)			(33.4)
Repurchase of common stock (in shares)	(3.5)
Dividends paid to JCG shareholders		(39.8)			(39.8)
Balance at Dec. 31, 2013	$ 1.9	1,496.0	(1.1)	13.7	1,510.5
Balance (in shares) at Dec. 31, 2013	188.6
Increase (Decrease) in Stockholders' Equity
Net income		154.4		1.1	155.5
Other comprehensive loss			(0.3)		(0.3)
Amortization of stock-based compensation		25.9		1.6	27.5
Issuance and forfeitures of restricted stock awards, net (in shares)	2.7
Stock option exercises and employee stock purchases		8.4			8.4
Stock option exercises and employee stock purchases (in shares)	0.9
Changes in noncontrolling interests in consolidated investment products				32.2	32.2
Distributions to noncontrolling interests				(1.0)	(1.0)
Change in fair value of redeemable noncontrolling interests		1.2			1.2
Vesting of nonredeemable noncontrolling interests				0.6	0.6
Purchase of noncontrolling interests				(0.9)	(0.9)
Repurchase of common stock		(87.2)			(87.2)
Repurchase of common stock (in shares)	(7.0)
Dividends paid to JCG shareholders		(58.4)			(58.4)
Balance at Dec. 31, 2014	$ 1.9	1,540.3	(1.4)	47.3	1,588.1
Balance (in shares) at Dec. 31, 2014	185.2
Increase (Decrease) in Stockholders' Equity
Net income		155.8		2.4	158.2
Other comprehensive loss			(7.5)	(4.1)	(11.6)
Amortization of stock-based compensation		35.0		1.2	36.2
Issuance and forfeitures of restricted stock awards, net				(0.6)	(0.6)
Issuance and forfeitures of restricted stock awards, net (in shares)	2.9
Stock option exercises and employee stock purchases		11.0			11.0
Stock option exercises and employee stock purchases (in shares)	1.4
Tax impact of stock-based compensation		3.9			3.9
Noncontrolling interest from the acquisition of Kapstream				85.7	85.7
Changes in noncontrolling interests in consolidated investment products				(41.1)	(41.1)
Distributions to noncontrolling interests				(1.0)	(1.0)
Change in fair value of redeemable noncontrolling interests		0.7			0.7
Purchase of noncontrolling interests				(0.4)	(0.4)
Repurchase of common stock	$ (0.1)	(91.7)			(91.8)
Repurchase of common stock (in shares)	(5.8)
Dividends paid to JCG shareholders		(65.2)			(65.2)
Balance at Dec. 31, 2015	$ 1.8	$ 1,589.8	$ (8.9)	$ 89.4	$ 1,672.1
Balance (in shares) at Dec. 31, 2015	183.7