Fair Values of Assets and Liabilities (Tables) - Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member]
|
9 Months Ended |
Dec. 31, 2017 |
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |
|
| Fair Value Measurements, Recurring and Nonrecurring [Table Text Block] |
| | | | | | | | | | | | | | | | | | | | | | | | As of December 31, 2017 | | | Quoted prices in active markets
(Level 1) | | Significant other observable inputs
(Level 2) | | Significant unobservable inputs
(Level 3) | | Investments measured at NAV | | Total | Assets: | | | | | | | | | | | Cash equivalents:(1) | | | | | | | | | | | Money market funds | | $ | 289,214 |
| | $ | — |
| | $ | — |
| | $ | — |
| | $ | 289,214 |
| Time deposits and other | | — |
| | 12,317 |
| | — |
| | — |
| | 12,317 |
| Total cash equivalents | | 289,214 |
| | 12,317 |
| | — |
| | — |
| | 301,531 |
| Trading investments of proprietary fund products and other trading investments:(2) | | | | | | | | | | |
| Seed capital investments | | 120,329 |
| | 58,158 |
| | — |
| | 3,593 |
| | 182,080 |
| Other(3) | | 26,717 |
| | 2,556 |
| | — |
| | — |
| | 29,273 |
| Trading investments relating to long-term incentive compensation plans(4) | | 187,473 |
| | — |
| | — |
| | 103 |
| | 187,576 |
| Equity method investments relating to long-term incentive compensation plans(5) | | — |
| | — |
| | 1,431 |
| | 9,009 |
| | 10,440 |
| Total current investments(6) | | 334,519 |
| | 60,714 |
| | 1,431 |
| | 12,705 |
| | 409,369 |
| Equity method investments in partnerships and LLCs:(5)(7) | | | | | | | | | | | Seed capital investments(6) | | — |
| | — |
| | 891 |
| | 15,595 |
| | 16,486 |
| Seed capital investments in real estate funds | | — |
| | — |
| | 27,837 |
| | — |
| | 27,837 |
| Other | | — |
| | — |
| | — |
| | 12,569 |
| | 12,569 |
| Investments in partnerships and LLCs:(7) | | | | | | | | | |
|
| Seed capital investments | | — |
| | — |
| | — |
| | 3,287 |
| | 3,287 |
| Investments related to long-term incentive compensation plans | | — |
| | — |
| | 9,367 |
| | — |
| | 9,367 |
| Other | | — |
| | 102 |
| | 380 |
| | — |
| | 482 |
| Derivative assets(7)(8) | | 7,183 |
| | — |
| | — |
| | — |
| | 7,183 |
| Other investments(7) | | — |
| | — |
| | 112 |
| | — |
| | 112 |
| Total | | $ | 630,916 |
| | $ | 73,133 |
| | $ | 40,018 |
| | $ | 44,156 |
| | $ | 788,223 |
| Liabilities: | | | | | | | | | | | Contingent consideration liabilities(9) | | $ | — |
| | $ | — |
| | $ | (20,701 | ) | | $ | — |
| | $ | (20,701 | ) | Derivative liabilities(8) | | (2,288 | ) | | — |
| | — |
| | — |
| | (2,288 | ) | Total | | $ | (2,288 | ) | | $ | — |
| | $ | (20,701 | ) | | $ | — |
| | $ | (22,989 | ) |
| | | | | | | | | | | | | | | | | | | | | | | | As of March 31, 2017 | | | Quoted prices in active markets
(Level 1) | | Significant other observable inputs
(Level 2) | | Significant unobservable inputs
(Level 3) | | Investments measured at NAV | | Total | Assets: | | | | | | | | | | | Cash equivalents:(1) | | | | | | | | | | | Money market funds | | $ | 403,585 |
| | $ | — |
| | $ | — |
| | $ | — |
| | $ | 403,585 |
| Time deposits and other | | — |
| | 35,835 |
| | — |
| | — |
| | 35,835 |
| Total cash equivalents | | 403,585 |
| | 35,835 |
| | — |
| | — |
| | 439,420 |
| Trading investments of proprietary fund products and other trading investments:(2) | | | | | | | | | | | Seed capital investments | | 141,025 |
| | 75,275 |
| | — |
| | 4,373 |
| | 220,673 |
| Other(3) | | 39,177 |
| | 2,724 |
| | — |
| | 11 |
| | 41,912 |
| Trading investments relating to long-term incentive compensation plans(4) | | 150,576 |
| | — |
| | — |
| | 327 |
| | 150,903 |
| Equity method investments relating to proprietary fund products and long-term incentive compensation plans:(5) | | | | | | | | | |
|
| Seed capital investments | | — |
| | 2,502 |
| | — |
| | — |
| | 2,502 |
| Investments related to long-term incentive compensation plans | | — |
| | — |
| | 1,337 |
| | 6,292 |
| | 7,629 |
| Total current investments(6) | | 330,778 |
|
| 80,501 |
| | 1,337 |
| | 11,003 |
| | 423,619 |
| Equity method investments in partnerships and LLCs:(5)(7) | | | | | | | | | | | Seed capital investments(6) | | — |
| | — |
| | 752 |
| | 22,712 |
| | 23,464 |
| Seed capital investments in real estate funds | | — |
| | — |
| | 26,909 |
| | — |
| | 26,909 |
| Other | | — |
| | — |
| | 1,646 |
| | 15,617 |
| | 17,263 |
| Investments in partnerships and LLCs:(7) | | | | | | | | | | | Seed capital investments | | — |
| | — |
| | — |
| | 3,440 |
| | 3,440 |
| Investments related to long-term incentive compensation plans | | — |
| | — |
| | 9,315 |
| | — |
| | 9,315 |
| Other | | — |
| | 99 |
| | 1,825 |
| | — |
| | 1,924 |
| Derivative assets(7)(8) | | 2,718 |
| | — |
| | — |
| | — |
| | 2,718 |
| Other investments(7) | | — |
| | — |
| | 113 |
| | — |
| | 113 |
| Total | | $ | 737,081 |
| | $ | 116,435 |
| | $ | 41,897 |
| | $ | 52,772 |
| | $ | 948,185 |
| Liabilities: | | | | | | | | | | | Contingent consideration liabilities(9) | | $ | — |
| | $ | — |
| | $ | (36,810 | ) | | $ | — |
| | $ | (36,810 | ) | Derivative liabilities(8) | | (4,522 | ) | | — |
| | — |
| | — |
| | (4,522 | ) | Total | | $ | (4,522 | ) | | $ | — |
| | $ | (36,810 | ) | | $ | — |
| | $ | (41,332 | ) |
| | (1) | Cash equivalents include highly liquid investments with original maturities of 90 days or less. Cash investments in actively traded money market funds are classified as Level 1. Cash investments in time deposits and other are measured at amortized cost, which approximates fair value because of the short time between purchase of the instrument and its expected realization, and are classified as Level 2. |
| | (2) | Trading investments of proprietary fund products and other trading investments consist of approximately 77% and 23% equity and debt securities, respectively, as of December 31, 2017, and approximately 79% and 21% equity and debt securities, respectively, as of March 31, 2017. |
| | (3) | Includes $13,696 and $26,854 in noncontrolling interests associated with consolidated seed investment products as of December 31, 2017 and March 31, 2017, respectively. |
| | (4) | Primarily mutual funds where there is minimal market risk to the Company as any change in value is primarily offset by an adjustment to compensation expense and related deferred compensation liability. |
| | (5) | Certain of Legg Mason's equity method investments are investment companies that record underlying investments at fair value. Therefore, the fair value of these investments is measured using Legg Mason's share of the investee's underlying net income or loss, which is predominately representative of fair value adjustments in the investments held by the equity method investee. Other equity method investments not measured at fair value on a recurring basis are excluded from the tables above. |
| | (6) | Excludes $41,548 and $28,300 of seed capital as of December 31, 2017 and March 31, 2017, respectively, which is related to Legg Mason's investments in CIVs. See Note 13. |
| | (7) | Amounts are included in Other non-current assets in the Consolidated Balance Sheets for each of the periods presented. |
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| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block] |
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Balance as of September 30, 2017 | | Purchases | | Sales | | Redemptions/ Settlements/ Other | | Transfers | | Realized and unrealized gains/(losses), net | | Balance as of December 31, 2017 | Assets: | | | | | | | | | | | | | | | Equity method investments relating to long-term incentive compensation plans | | $ | 1,393 |
| | $ | 11 |
| | $ | — |
| | $ | (11 | ) | | $ | — |
| | $ | 38 |
| | $ | 1,431 |
| Equity method investments in partnerships and LLCs: | | | | | | | | | | | | | | | Seed capital investments | | 851 |
| | — |
| | — |
| | — |
| | — |
| | 40 |
| | 891 |
| Seed capital investments in real estate funds | | 27,382 |
| | 868 |
| | — |
| | (1,139 | ) | | — |
| | 726 |
| | 27,837 |
| Investments in partnerships and LLCs: | | | | | | | | | | | | | |
|
| Investments related to long-term incentive compensation plans | | 9,367 |
| | — |
| | — |
| | — |
| | — |
| | — |
| | 9,367 |
| Other proprietary fund products | | 485 |
| | — |
| | — |
| | (105 | ) | | — |
| | — |
| | 380 |
| Other investments | | 114 |
| | — |
| | — |
| | — |
| | — |
| | (2 | ) | | 112 |
| | | $ | 39,592 |
| | $ | 879 |
| | $ | — |
| | $ | (1,255 | ) | | $ | — |
| | $ | 802 |
| | $ | 40,018 |
| Liabilities: | | | | | | | | | | | | | | | Contingent consideration liabilities | | $ | (21,162 | ) | | $ | (1,900 | ) | | n/a |
| | $ | 3,242 |
| | n/a |
| | $ | (881 | ) | | $ | (20,701 | ) |
n/a - not applicable
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Balance as of September 30, 2016 | | Purchases | | Sales | | Redemptions/ Settlements/ Other | | Transfers | | Realized and unrealized gains/(losses), net | | Balance as of December 31, 2016 | Assets: | | | | | | | | | | | | | | | Equity method investments relating to long-term incentive compensation plans | | $ | 2,653 |
| | $ | 20 |
| | $ | — |
| | $ | (20 | ) | | $ | — |
| | $ | 48 |
| | $ | 2,701 |
| Equity method investments in partnerships and LLCs: | |
|
| |
|
| |
|
| |
|
| |
|
| |
|
| |
|
| Seed capital investments | | 552 |
| | — |
| | — |
| | — |
| | — |
| | 39 |
| | 591 |
| Seed capital investments in real estate funds | | 25,722 |
| | 667 |
| | — |
| | (197 | ) | | — |
| | 487 |
| | 26,679 |
| Investments in partnerships and LLCs: | | | | | | | | | | | | | | | Investments related to long-term incentive compensation plans | | 7,501 |
| | 314 |
| | — |
| | — |
| | — |
| | — |
| | 7,815 |
| Other proprietary fund products | | 3,827 |
| | — |
| | — |
| | (2,000 | ) | | — |
| | 541 |
| | 2,368 |
| Other investments | | 245 |
| | — |
| | — |
| | — |
| | — |
| | (83 | ) | | 162 |
| | | $ | 40,500 |
| | $ | 1,001 |
| | $ | — |
| | $ | (2,217 | ) | | $ | — |
| | $ | 1,032 |
| | $ | 40,316 |
| Liabilities: | | | | | | | | | | | | | | | Contingent consideration liabilities | | $ | (52,053 | ) | | $ | — |
| | n/a |
| | $ | — |
| | n/a |
| | $ | 16,569 |
| | $ | (35,484 | ) |
n/a - not applicable
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Balance as of March 31, 2017 | | Purchases | | Sales | | Redemptions/ Settlements/ Other | | Transfers | | Realized and unrealized gains/(losses), net | | Balance as of December 31, 2017 | Assets: | | | | | | | | | | | | | | | Equity method investments relating to long-term incentive compensation plans | | $ | 1,337 |
| | $ | 33 |
| | $ | — |
| | $ | (33 | ) | | $ | — |
| | $ | 94 |
| | $ | 1,431 |
| Equity method investments in partnerships and LLCs: | | | | | | | | | | | | | | | Seed capital investments | | 752 |
| | — |
| | — |
| | — |
| | — |
| | 139 |
| | 891 |
| Seed capital investments in real estate funds | | 26,909 |
| | 3,063 |
| | — |
| | (3,889 | ) | | — |
| | 1,754 |
| | 27,837 |
| Other proprietary fund products | | 1,646 |
| | — |
| | — |
| | (1,646 | ) | | — |
| | — |
| | — |
| Investments in partnerships and LLCs: | | | | | | | | | | | | | |
|
| Investments related to long-term incentive compensation plans | | 9,315 |
| | 52 |
| | — |
| | — |
| | — |
| | — |
| | 9,367 |
| Other proprietary fund products | | 1,825 |
| | — |
| | — |
| | (1,510 | ) | | — |
| | 65 |
| | 380 |
| Other investments | | 113 |
| | — |
| | — |
| | — |
| | — |
| | (1 | ) | | 112 |
| | | $ | 41,897 |
|
| $ | 3,148 |
|
| $ | — |
|
| $ | (7,078 | ) |
| $ | — |
|
| $ | 2,051 |
| | $ | 40,018 |
| Liabilities: | | | | | | | | | | | | | | | Contingent consideration liabilities | | $ | (36,810 | ) | | $ | (1,900 | ) | | n/a |
| | $ | 3,242 |
| | n/a |
| | $ | 14,767 |
| | $ | (20,701 | ) |
n/a - not applicable
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Balance as of March 31, 2016 | | Purchases | | Sales | | Redemptions/Settlements/ Other | | Transfers | | Realized and unrealized gains/(losses), net | | Balance as of December 31,
2016 | Assets: | | | | | | | | | | | | | | | Trading investments of seed capital investments in proprietary fund products | | $ | 3 |
| | $ | — |
| | $ | — |
| | $ | (3 | ) | | $ | — |
| | $ | — |
| | $ | — |
| Equity method investments relating to long-term incentive compensation plans | | — |
| | 2,979 |
| | — |
| | (448 | ) | | — |
| | 170 |
| | 2,701 |
| Equity method investments in partnerships and LLCs: | | | | | | | | | | | | | |
|
| Seed capital investments | | 627 |
| | — |
| | — |
| | — |
| | — |
| | (36 | ) | | 591 |
| Seed capital investments in real estate funds | | — |
| | 25,966 |
| | — |
| | (636 | ) | | — |
| | 1,349 |
| | 26,679 |
| Investments in partnerships and LLCs: | | | | | | | | | | | | | | | Investments related to long-term incentive compensation plans | | 7,501 |
| | 314 |
| | — |
| | — |
| | — |
| | — |
| | 7,815 |
| Other proprietary fund products | | 4,807 |
| | — |
| | — |
| | (3,000 | ) | | — |
| | 561 |
| | 2,368 |
| Other investments | | 83 |
| | — |
| | — |
| | — |
| | — |
| | 79 |
| | 162 |
| | | $ | 13,021 |
| | $ | 29,259 |
| | $ | — |
| | $ | (4,087 | ) | | $ | — |
| | $ | 2,123 |
| | $ | 40,316 |
| Liabilities: | | | | | | | | | | | | | | | Contingent consideration liabilities | | $ | (84,585 | ) | | $ | (2,000 | ) | | n/a |
| | $ | 6,587 |
| | n/a |
| | $ | 44,514 |
| | $ | (35,484 | ) |
|
| Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Table Text Block] |
| | | | | | | | | | | | | | | | | | | | | | Fair Value Determined Using NAV | | As of December 31, 2017 | Category of Investment | | Investment Strategy | | December 31, 2017 | | March 31, 2017 | | Unfunded Commitments | | Remaining Term | Funds-of-hedge funds | | Global macro, fixed income, long/short equity, natural resources, systematic, emerging market, European hedge | | $ | 11,024 |
| (1) | $ | 18,537 |
| | n/a |
| | n/a | Hedge funds | | Fixed income - developed market, event driven, fixed income - hedge, relative value arbitrage, European hedge | | 9,760 |
| | 10,107 |
| | $ | 20,000 |
| | n/a | Private equity funds | | Long/short equity | | 14,231 |
| (2) | 17,612 |
| | 6,589 |
| | Up to 11 years | Equity method | | Long/short fixed income | | 9,009 |
| | 6,292 |
| | n/a |
| | n/a | Other | | Various | | 132 |
| | 224 |
| | n/a |
| | Various (3) | Total | | | | $ | 44,156 |
| | $ | 52,772 |
| | $ | 26,589 |
| | |
n/a - not applicable | | (1) | Liquidation restrictions: 1% daily redemption, 20% monthly redemption, 11% quarterly redemption, and 68% are not subject to redemption or are not currently redeemable. |
| | (2) | Liquidations are expected over the remaining term. |
| | (3) | Of this balance, 34% has a remaining term of less than one year and 66% has a remaining term of 14 years. |
|