OTHER COMPREHENSIVE INCOME AND ACCUMULATED OTHER COMPREHENSIVE INCOME. (Accumulated Other Comprehensive Income) (Detail) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended |
Jun. 30, 2015 | Jun. 30, 2014 | Jun. 30, 2015 | Jun. 30, 2014 |
Changes in each component of accumulated other comprehensive income | | | | |
Balances at December 31, 2014 | | | $ 136.4 | |
Other comprehensive income (loss) before reclassifications and income taxes | | | 18 | |
Reclassification adjustments related to net gains realized on dispositions recognized in non-operating investment income, determined using average cost | | | (39.3) | |
Other comprehensive income (loss) before income taxes | $ (19.5) | $ 30.5 | (21.3) | $ 23.4 |
Deferred tax benefits (income taxes) | 7.1 | (11.6) | 10.7 | (8.8) |
Total other comprehensive income (loss) | (12.4) | $ 18.9 | (10.6) | $ 14.6 |
Balances at June 30, 2015 | 125.8 | | 125.8 | |
Net unrealized holding gains [Member] | | | | |
Changes in each component of accumulated other comprehensive income | | | | |
Balances at December 31, 2014 | | | 165.5 | |
Other comprehensive income (loss) before reclassifications and income taxes | | | 22.1 | |
Reclassification adjustments related to net gains realized on dispositions recognized in non-operating investment income, determined using average cost | | | (39.3) | |
Other comprehensive income (loss) before income taxes | | | (17.2) | |
Deferred tax benefits (income taxes) | | | 9.2 | |
Total other comprehensive income (loss) | | | (8) | |
Balances at June 30, 2015 | 157.5 | | 157.5 | |
Net unrealized holding gains [Member] | Investments in sponsored funds [Member] | | | | |
Changes in each component of accumulated other comprehensive income | | | | |
Balances at December 31, 2014 | | | 165 | |
Other comprehensive income (loss) before reclassifications and income taxes | | | 21.9 | |
Reclassification adjustments related to net gains realized on dispositions recognized in non-operating investment income, determined using average cost | | | (39.3) | |
Other comprehensive income (loss) before income taxes | | | (17.4) | |
Deferred tax benefits (income taxes) | | | 9.3 | |
Total other comprehensive income (loss) | | | (8.1) | |
Balances at June 30, 2015 | 156.9 | | 156.9 | |
Net unrealized holding gains [Member] | Equity share of UTI’s net unrealized holding gains [Member] | | | | |
Changes in each component of accumulated other comprehensive income | | | | |
Balances at December 31, 2014 | | | 0.5 | |
Other comprehensive income (loss) before reclassifications and income taxes | | | 0.2 | |
Reclassification adjustments related to net gains realized on dispositions recognized in non-operating investment income, determined using average cost | | | 0 | |
Other comprehensive income (loss) before income taxes | | | 0.2 | |
Deferred tax benefits (income taxes) | | | (0.1) | |
Total other comprehensive income (loss) | | | 0.1 | |
Balances at June 30, 2015 | 0.6 | | 0.6 | |
Currency translation adjustments [Member] | | | | |
Changes in each component of accumulated other comprehensive income | | | | |
Balances at December 31, 2014 | | | (29.1) | |
Other comprehensive income (loss) before reclassifications and income taxes | | | (4.1) | |
Reclassification adjustments related to net gains realized on dispositions recognized in non-operating investment income, determined using average cost | | | 0 | |
Other comprehensive income (loss) before income taxes | | | (4.1) | |
Deferred tax benefits (income taxes) | | | 1.5 | |
Total other comprehensive income (loss) | | | (2.6) | |
Balances at June 30, 2015 | $ (31.7) | | $ (31.7) | |