Fair Value Measurements - Changes in Level 3 Fair Value Measurements (Details) - Recurring Fair Value Measurements - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended |
Jun. 30, 2017 | Jun. 30, 2016 | Jun. 30, 2017 | Jun. 30, 2016 |
Available-for-sale | Fixed maturities | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, assets | $ 398.5 | $ 392.7 | $ 517.4 | $ 378.8 |
Total realized/unrealized gains (losses) included in net income, assets | (4.5) | (0.2) | (7.7) | (0.4) |
Total realized/unrealized gains (losses) included in other comprehensive income, assets | 6.2 | (0.8) | 8.9 | (1.7) |
Net purchases, sales, issuances and settlements, assets | (0.5) | 19.5 | (30) | 38.5 |
Transfers into Level 3, assets | 123.3 | 15.7 | 128.6 | 15.7 |
Transfers out of Level 3, assets | (62.6) | (32.6) | (156.8) | (36.6) |
Ending balance, assets | 460.4 | 394.3 | 460.4 | 394.3 |
Changes in unrealized gains (losses) included in net income relating to positions still held, assets | (4.8) | (0.2) | (5) | (0.4) |
Gross purchases, sales, issuances and settlements | | | | |
Purchases, assets | 27.6 | 24.2 | 67.4 | 64.8 |
Sales, assets | (14) | | (69.1) | (9.3) |
Settlements, assets | (14.1) | (4.7) | (28.3) | (17) |
Net purchases, sales, issuances and settlements, assets | (0.5) | 19.5 | (30) | 38.5 |
Available-for-sale | Non-U.S. governments | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, assets | 66.5 | 97.8 | 62.1 | 79.1 |
Total realized/unrealized gains (losses) included in net income, assets | | | (0.1) | (0.1) |
Total realized/unrealized gains (losses) included in other comprehensive income, assets | (0.1) | | 0.2 | 2.5 |
Net purchases, sales, issuances and settlements, assets | (1.3) | 2.3 | 2.9 | 18.6 |
Transfers out of Level 3, assets | | (32.6) | | (32.6) |
Ending balance, assets | 65.1 | 67.5 | 65.1 | 67.5 |
Changes in unrealized gains (losses) included in net income relating to positions still held, assets | (0.1) | | (0.1) | (0.1) |
Gross purchases, sales, issuances and settlements | | | | |
Purchases, assets | | 2.6 | 21.8 | 19.3 |
Sales, assets | (0.9) | | (18.2) | |
Settlements, assets | (0.4) | (0.3) | (0.7) | (0.7) |
Net purchases, sales, issuances and settlements, assets | (1.3) | 2.3 | 2.9 | 18.6 |
Available-for-sale | Corporate debt securities | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, assets | 235.3 | 222.7 | 259.1 | 223.9 |
Total realized/unrealized gains (losses) included in net income, assets | (0.1) | (0.2) | (1.9) | (0.3) |
Total realized/unrealized gains (losses) included in other comprehensive income, assets | (0.8) | (1.1) | (0.4) | (3.7) |
Net purchases, sales, issuances and settlements, assets | (11.8) | 4.6 | (38.8) | 7.8 |
Transfers into Level 3, assets | 17.6 | 15.7 | 22.2 | 15.7 |
Transfers out of Level 3, assets | (37.3) | | (37.3) | (1.7) |
Ending balance, assets | 202.9 | 241.7 | 202.9 | 241.7 |
Changes in unrealized gains (losses) included in net income relating to positions still held, assets | (0.2) | (0.2) | (0.4) | (0.3) |
Gross purchases, sales, issuances and settlements | | | | |
Purchases, assets | 14.6 | 7.9 | 32.6 | 31.8 |
Sales, assets | (13.1) | | (50.9) | (9.3) |
Settlements, assets | (13.3) | (3.3) | (20.5) | (14.7) |
Net purchases, sales, issuances and settlements, assets | (11.8) | 4.6 | (38.8) | 7.8 |
Available-for-sale | Commercial mortgage-backed securities | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, assets | 62.7 | 2.4 | 71.1 | 4.8 |
Total realized/unrealized gains (losses) included in net income, assets | (4.5) | | (5.7) | |
Total realized/unrealized gains (losses) included in other comprehensive income, assets | 7.2 | | 9.8 | |
Net purchases, sales, issuances and settlements, assets | 0.5 | 13.1 | (0.5) | 13 |
Transfers into Level 3, assets | 17.3 | | 18 | |
Transfers out of Level 3, assets | (21.7) | | (31.2) | (2.3) |
Ending balance, assets | 61.5 | 15.5 | 61.5 | 15.5 |
Changes in unrealized gains (losses) included in net income relating to positions still held, assets | (4.5) | | (4.5) | |
Gross purchases, sales, issuances and settlements | | | | |
Purchases, assets | | 13.7 | | 13.7 |
Settlements, assets | 0.5 | (0.6) | (0.5) | (0.7) |
Net purchases, sales, issuances and settlements, assets | 0.5 | 13.1 | (0.5) | 13 |
Available-for-sale | Collateralized debt obligations | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, assets | 27.5 | 62.8 | 33.6 | 63.5 |
Total realized/unrealized gains (losses) included in other comprehensive income, assets | | 0.2 | (0.7) | (0.5) |
Net purchases, sales, issuances and settlements, assets | 12.3 | (0.2) | 6.9 | (0.2) |
Transfers into Level 3, assets | 88.3 | | 88.3 | |
Ending balance, assets | 128.1 | 62.8 | 128.1 | 62.8 |
Gross purchases, sales, issuances and settlements | | | | |
Purchases, assets | 13 | | 13 | |
Settlements, assets | (0.7) | (0.2) | (6.1) | (0.2) |
Net purchases, sales, issuances and settlements, assets | 12.3 | (0.2) | 6.9 | (0.2) |
Available-for-sale | Other debt obligations | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, assets | 6.5 | 7 | 91.5 | 7.5 |
Total realized/unrealized gains (losses) included in net income, assets | 0.1 | | | |
Total realized/unrealized gains (losses) included in other comprehensive income, assets | (0.1) | 0.1 | | |
Net purchases, sales, issuances and settlements, assets | (0.2) | (0.3) | (0.5) | (0.7) |
Transfers into Level 3, assets | 0.1 | | 0.1 | |
Transfers out of Level 3, assets | (3.6) | | (88.3) | |
Ending balance, assets | 2.8 | 6.8 | 2.8 | 6.8 |
Gross purchases, sales, issuances and settlements | | | | |
Settlements, assets | (0.2) | (0.3) | (0.5) | (0.7) |
Net purchases, sales, issuances and settlements, assets | (0.2) | (0.3) | (0.5) | (0.7) |
Available-for-sale | Equity securities | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, assets | 2.7 | 4.1 | 2.7 | 4.1 |
Total realized/unrealized gains (losses) included in net income, assets | | (1.3) | | (1.3) |
Total realized/unrealized gains (losses) included in other comprehensive income, assets | | (0.1) | | (0.1) |
Ending balance, assets | 2.7 | 2.7 | 2.7 | 2.7 |
Changes in unrealized gains (losses) included in net income relating to positions still held, assets | | (1.4) | | (1.4) |
Trading | Fixed maturities | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, assets | | 135.8 | 92.9 | 135.5 |
Total realized/unrealized gains (losses) included in net income, assets | | | (2.4) | 0.3 |
Net purchases, sales, issuances and settlements, assets | | (18) | (92.4) | (18) |
Transfers into Level 3, assets | | | 1.9 | |
Ending balance, assets | | 117.8 | | 117.8 |
Changes in unrealized gains (losses) included in net income relating to positions still held, assets | | | (0.2) | 0.4 |
Gross purchases, sales, issuances and settlements | | | | |
Sales, assets | | (18) | | (18) |
Settlements, assets | | | (92.4) | |
Net purchases, sales, issuances and settlements, assets | | (18) | (92.4) | (18) |
Trading | Equity securities | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, assets | 0.6 | | | |
Total realized/unrealized gains (losses) included in net income, assets | 0.1 | | | |
Net purchases, sales, issuances and settlements, assets | (0.7) | | (0.7) | |
Transfers into Level 3, assets | | | 0.7 | |
Gross purchases, sales, issuances and settlements | | | | |
Settlements, assets | (0.7) | | (0.7) | |
Net purchases, sales, issuances and settlements, assets | (0.7) | | (0.7) | |
Derivative assets | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, assets | 30.8 | 59.1 | 33.9 | 47.2 |
Total realized/unrealized gains (losses) included in net income, assets | (0.9) | 1.7 | (4.1) | 13.2 |
Net purchases, sales, issuances and settlements, assets | 1.7 | 0.3 | 1.8 | 0.7 |
Ending balance, assets | 31.6 | 61.1 | 31.6 | 61.1 |
Changes in unrealized gains (losses) included in net income relating to positions still held, assets | (0.5) | 2.4 | (3.8) | 14.4 |
Gross purchases, sales, issuances and settlements | | | | |
Purchases, assets | 1.9 | | 2.2 | |
Sales, assets | (0.2) | 0.3 | (0.4) | 0.7 |
Net purchases, sales, issuances and settlements, assets | 1.7 | 0.3 | 1.8 | 0.7 |
Other investments | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, assets | 38.3 | 35.9 | 36.9 | 35.1 |
Total realized/unrealized gains (losses) included in net income, assets | 0.7 | 0.1 | 1.9 | 0.7 |
Net purchases, sales, issuances and settlements, assets | (3.8) | 0.1 | (3.6) | 0.3 |
Ending balance, assets | 35.2 | 36.1 | 35.2 | 36.1 |
Changes in unrealized gains (losses) included in net income relating to positions still held, assets | 0.7 | 0.1 | 1.9 | 0.7 |
Gross purchases, sales, issuances and settlements | | | | |
Purchases, assets | 0.3 | 0.1 | 0.5 | 0.3 |
Sales, assets | (4.1) | | (4.1) | |
Net purchases, sales, issuances and settlements, assets | (3.8) | 0.1 | (3.6) | 0.3 |
Separate account assets | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, assets | 7,257.6 | 7,094.5 | 7,354.8 | 7,013.9 |
Total realized/unrealized gains (losses) included in net income, assets | 194.4 | 140.2 | 358.2 | 293.1 |
Total realized/unrealized gains (losses) included in other comprehensive income, assets | (0.6) | | (0.9) | (0.1) |
Net purchases, sales, issuances and settlements, assets | (19.1) | 174.2 | (278.9) | 101.2 |
Transfers into Level 3, assets | 2.1 | 0.1 | 2.1 | 0.9 |
Transfers out of Level 3, assets | (21.5) | (0.7) | (22.4) | (0.7) |
Ending balance, assets | 7,412.9 | 7,408.3 | 7,412.9 | 7,408.3 |
Changes in unrealized gains (losses) included in net income relating to positions still held, assets | 168.2 | 95.9 | 323.5 | 305.7 |
Gross purchases, sales, issuances and settlements | | | | |
Purchases, assets | 120.7 | 233.9 | 179.3 | 290.1 |
Sales, assets | (70.9) | (5.4) | (381.4) | (66.1) |
Issuances, assets | (64.4) | (47.2) | (135.7) | (140) |
Settlements, assets | (4.5) | (7.1) | 58.9 | 17.2 |
Net purchases, sales, issuances and settlements, assets | (19.1) | 174.2 | (278.9) | 101.2 |
Investment contracts | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, liabilities | (119.6) | (213) | (176.5) | (177.4) |
Total realized/unrealized gains (losses) included in net income, liabilities | (29.1) | (113) | 23.5 | (151.3) |
Total realized/unrealized gains (losses) included in other comprehensive income, liabilities | 0.2 | | 0.3 | |
Net purchases, sales, issuances and settlements, liabilities | 1.9 | 1.7 | 6.1 | 4.4 |
Ending balance, liabilities | (146.6) | (324.3) | (146.6) | (324.3) |
Changes in unrealized gains (losses) included in net income relating to positions still held, liabilities | (29.7) | (114.3) | 21.6 | (153.4) |
Gross purchases, sales, issuances and settlements | | | | |
Issuances, liabilities | 0.2 | | 0.4 | 1.1 |
Settlements, liabilities | 1.7 | 1.7 | 5.7 | 3.3 |
Net purchases, sales, issuances and settlements, liabilities | 1.9 | 1.7 | 6.1 | 4.4 |
Derivative liabilities | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, liabilities | (18.1) | (36.1) | (22.6) | (50.5) |
Total realized/unrealized gains (losses) included in net income, liabilities | 6.5 | 6.9 | 11.1 | 20.5 |
Total realized/unrealized gains (losses) included in other comprehensive income, liabilities | | | | 0.5 |
Net purchases, sales, issuances and settlements, liabilities | (1) | 0.7 | (1.1) | 1 |
Ending balance, liabilities | (12.6) | (28.5) | (12.6) | (28.5) |
Changes in unrealized gains (losses) included in net income relating to positions still held, liabilities | 6.4 | 5.1 | 9.5 | 17.3 |
Gross purchases, sales, issuances and settlements | | | | |
Purchases, liabilities | (1) | | (1.2) | |
Sales, liabilities | | 0.7 | 0.1 | 1 |
Net purchases, sales, issuances and settlements, liabilities | $ (1) | 0.7 | (1.1) | 1 |
Other liabilities | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, liabilities | | (73.1) | (59.9) | (68.1) |
Total realized/unrealized gains (losses) included in net income, liabilities | | (2.9) | (0.1) | (7.9) |
Net purchases, sales, issuances and settlements, liabilities | | 17.4 | 60 | 17.4 |
Ending balance, liabilities | | (58.6) | | (58.6) |
Changes in unrealized gains (losses) included in net income relating to positions still held, liabilities | | (2.4) | | (6.2) |
Gross purchases, sales, issuances and settlements | | | | |
Sales, liabilities | | 17.4 | | 17.4 |
Settlements, liabilities | | | 60 | |
Net purchases, sales, issuances and settlements, liabilities | | $ 17.4 | $ 60 | $ 17.4 |