Fair Value Measurements - Changes in Level 3 Fair Value Measurements (Details) - Recurring Fair Value Measurements - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended |
Sep. 30, 2016 | Sep. 30, 2015 | Sep. 30, 2016 | Sep. 30, 2015 |
Available-for-sale | Fixed maturities | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, assets | $ 394.3 | $ 377.3 | $ 378.8 | $ 412.2 |
Total realized/unrealized gains (losses) included in net income, assets | (0.4) | (0.1) | (0.8) | (0.3) |
Total realized/unrealized gains (losses) included in other comprehensive income, assets | 0.8 | (1.1) | (0.9) | (2.1) |
Net purchases, sales, issuances and settlements, assets | 32.4 | 26.7 | 70.9 | 58.6 |
Transfers into Level 3, assets | | 15 | 15.7 | 41.2 |
Transfers out of Level 3, assets | | (40.1) | (36.6) | (131.9) |
Ending balance, assets | 427.1 | 377.7 | 427.1 | 377.7 |
Changes in unrealized gains (losses) included in net income relating to positions still held, assets | (0.2) | (0.2) | (0.8) | (0.4) |
Gross purchases, sales, issuances and settlements | | | | |
Purchases, assets | 53.9 | 30.5 | 118.7 | 89.7 |
Sales, assets | (4.8) | | (14.1) | (5.7) |
Settlements, assets | (16.7) | (3.8) | (33.7) | (25.4) |
Net purchases, sales, issuances and settlements, assets | 32.4 | 26.7 | 70.9 | 58.6 |
Available-for-sale | Non-U.S. governments | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, assets | 67.5 | 45.6 | 79.1 | 38.7 |
Total realized/unrealized gains (losses) included in net income, assets | (0.1) | (0.1) | (0.2) | (0.2) |
Total realized/unrealized gains (losses) included in other comprehensive income, assets | 0.2 | 0.3 | 2.7 | 0.4 |
Net purchases, sales, issuances and settlements, assets | (3.8) | 3.1 | 14.8 | 10 |
Transfers out of Level 3, assets | | | (32.6) | |
Ending balance, assets | 63.8 | 48.9 | 63.8 | 48.9 |
Changes in unrealized gains (losses) included in net income relating to positions still held, assets | (0.1) | (0.1) | (0.2) | (0.2) |
Gross purchases, sales, issuances and settlements | | | | |
Purchases, assets | | 3.4 | 19.3 | 10.9 |
Sales, assets | (3.4) | | (3.4) | |
Settlements, assets | (0.4) | (0.3) | (1.1) | (0.9) |
Net purchases, sales, issuances and settlements, assets | (3.8) | 3.1 | 14.8 | 10 |
Available-for-sale | Corporate debt securities | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, assets | 241.7 | 227 | 223.9 | 245.6 |
Total realized/unrealized gains (losses) included in net income, assets | (0.3) | (0.1) | (0.6) | (0.2) |
Total realized/unrealized gains (losses) included in other comprehensive income, assets | (0.4) | (2.4) | (4.1) | (3.3) |
Net purchases, sales, issuances and settlements, assets | 18.1 | 3.4 | 25.9 | 27.1 |
Transfers into Level 3, assets | | 15 | 15.7 | 41.2 |
Transfers out of Level 3, assets | | (6.1) | (1.7) | (73.6) |
Ending balance, assets | 259.1 | 236.8 | 259.1 | 236.8 |
Changes in unrealized gains (losses) included in net income relating to positions still held, assets | (0.1) | (0.1) | (0.6) | (0.2) |
Gross purchases, sales, issuances and settlements | | | | |
Purchases, assets | 22.6 | 5.5 | 54.4 | 47.1 |
Sales, assets | (1.4) | | (10.7) | (5.7) |
Settlements, assets | (3.1) | (2.1) | (17.8) | (14.3) |
Net purchases, sales, issuances and settlements, assets | 18.1 | 3.4 | 25.9 | 27.1 |
Available-for-sale | Commercial mortgage-backed securities | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, assets | 15.5 | | 4.8 | |
Total realized/unrealized gains (losses) included in other comprehensive income, assets | 0.7 | 0.1 | 0.7 | 0.1 |
Net purchases, sales, issuances and settlements, assets | 10 | 15.2 | 23 | 15.2 |
Transfers out of Level 3, assets | | | (2.3) | |
Ending balance, assets | 26.2 | 15.3 | 26.2 | 15.3 |
Gross purchases, sales, issuances and settlements | | | | |
Purchases, assets | 11.3 | 15.2 | 25 | 15.2 |
Settlements, assets | (1.3) | | (2) | |
Net purchases, sales, issuances and settlements, assets | 10 | 15.2 | 23 | 15.2 |
Available-for-sale | Collateralized debt obligations | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, assets | 62.8 | 63.3 | 63.5 | 64.2 |
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) | | (0.6) | (0.1) |
Net purchases, sales, issuances and settlements, assets | (10.5) | (0.2) | (10.7) | (1) |
Ending balance, assets | 52.2 | 63.2 | 52.2 | 63.2 |
Gross purchases, sales, issuances and settlements | | | | |
Settlements, assets | (10.5) | (0.2) | (10.7) | (1) |
Net purchases, sales, issuances and settlements, assets | (10.5) | (0.2) | (10.7) | (1) |
Available-for-sale | Other debt obligations | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, assets | 6.8 | 41.4 | 7.5 | 63.7 |
Total realized/unrealized gains (losses) included in other comprehensive income, assets | 0.4 | 0.9 | 0.4 | 0.8 |
Net purchases, sales, issuances and settlements, assets | 18.6 | 5.2 | 17.9 | 7.3 |
Transfers out of Level 3, assets | | (34) | | (58.3) |
Ending balance, assets | 25.8 | 13.5 | 25.8 | 13.5 |
Gross purchases, sales, issuances and settlements | | | | |
Purchases, assets | 20 | 6.4 | 20 | 16.5 |
Settlements, assets | (1.4) | (1.2) | (2.1) | (9.2) |
Net purchases, sales, issuances and settlements, assets | 18.6 | 5.2 | 17.9 | 7.3 |
Available-for-sale | Equity securities | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, assets | 2.7 | 4.1 | 4.1 | 4.1 |
Total realized/unrealized gains (losses) included in net income, assets | | | (1.3) | |
Total realized/unrealized gains (losses) included in other comprehensive income, assets | | | (0.1) | |
Ending balance, assets | 2.7 | 4.1 | 2.7 | 4.1 |
Changes in unrealized gains (losses) included in net income relating to positions still held, assets | | | (1.4) | |
Trading | Fixed maturities | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, assets | 117.8 | 139.8 | 135.5 | 139.7 |
Total realized/unrealized gains (losses) included in net income, assets | 0.1 | (0.8) | 0.4 | (0.6) |
Net purchases, sales, issuances and settlements, assets | (0.1) | | (18.1) | (0.1) |
Ending balance, assets | 117.8 | 139 | 117.8 | 139 |
Changes in unrealized gains (losses) included in net income relating to positions still held, assets | (0.1) | (0.8) | 0.4 | (0.7) |
Gross purchases, sales, issuances and settlements | | | | |
Sales, assets | | | (18) | (0.2) |
Settlements, assets | (0.1) | | (0.1) | 0.1 |
Net purchases, sales, issuances and settlements, assets | (0.1) | | (18.1) | (0.1) |
Derivative assets | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, assets | 61.1 | 45.1 | 47.2 | 53.7 |
Total realized/unrealized gains (losses) included in net income, assets | (4.2) | 7.4 | 9 | (3.6) |
Net purchases, sales, issuances and settlements, assets | 0.5 | | 1.2 | 2.4 |
Ending balance, assets | 57.4 | 52.5 | 57.4 | 52.5 |
Changes in unrealized gains (losses) included in net income relating to positions still held, assets | (3.9) | 7.4 | 10.5 | (3.4) |
Gross purchases, sales, issuances and settlements | | | | |
Purchases, assets | 0.3 | | 0.3 | 2.5 |
Sales, assets | 0.2 | | 0.9 | (0.1) |
Net purchases, sales, issuances and settlements, assets | 0.5 | | 1.2 | 2.4 |
Other investments | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, assets | 36.1 | 29.7 | 35.1 | 127.2 |
Total realized/unrealized gains (losses) included in net income, assets | 0.6 | 0.5 | 1.3 | 4.5 |
Net purchases, sales, issuances and settlements, assets | 0.1 | 1.3 | 0.4 | (65.2) |
Transfers out of Level 3, assets | | | | (35) |
Ending balance, assets | 36.8 | 31.5 | 36.8 | 31.5 |
Changes in unrealized gains (losses) included in net income relating to positions still held, assets | 0.7 | 0.5 | 1.4 | 4.5 |
Gross purchases, sales, issuances and settlements | | | | |
Purchases, assets | 0.1 | 1.3 | 0.4 | 2.5 |
Sales, assets | | | | (67.7) |
Net purchases, sales, issuances and settlements, assets | 0.1 | 1.3 | 0.4 | (65.2) |
Separate account assets | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, assets | 7,408.3 | 6,406 | 7,013.9 | 5,891.4 |
Total realized/unrealized gains (losses) included in net income, assets | 233.5 | 344.4 | 526.6 | 799.3 |
Total realized/unrealized gains (losses) included in other comprehensive income, assets | | | (0.1) | |
Net purchases, sales, issuances and settlements, assets | (39.3) | (14.3) | 61.9 | 45.4 |
Transfers into Level 3, assets | | 0.1 | 0.9 | 0.2 |
Transfers out of Level 3, assets | (0.1) | (0.1) | (0.8) | (0.2) |
Ending balance, assets | 7,602.4 | 6,736.1 | 7,602.4 | 6,736.1 |
Changes in unrealized gains (losses) included in net income relating to positions still held, assets | 196.9 | 267.5 | 495.3 | 705.2 |
Gross purchases, sales, issuances and settlements | | | | |
Purchases, assets | 109 | 69.6 | 399.1 | 430.6 |
Sales, assets | (86.5) | (29.7) | (152.6) | (189.1) |
Issuances, assets | (140) | (54.7) | (280) | (200.5) |
Settlements, assets | 78.2 | 0.5 | 95.4 | 4.4 |
Net purchases, sales, issuances and settlements, assets | (39.3) | (14.3) | 61.9 | 45.4 |
Investment contracts | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, liabilities | (324.3) | (117) | (177.4) | (176.4) |
Total realized/unrealized gains (losses) included in net income, liabilities | (2.7) | (98.1) | (154) | (40.5) |
Net purchases, sales, issuances and settlements, liabilities | 0.6 | 4.8 | 5 | 6.6 |
Ending balance, liabilities | (326.4) | (210.3) | (326.4) | (210.3) |
Changes in unrealized gains (losses) included in net income relating to positions still held, liabilities | (4.7) | (98.9) | (158.3) | (43.8) |
Gross purchases, sales, issuances and settlements | | | | |
Issuances, liabilities | (0.6) | 3.7 | 0.5 | 1.4 |
Settlements, liabilities | 1.2 | 1.1 | 4.5 | 5.2 |
Net purchases, sales, issuances and settlements, liabilities | 0.6 | 4.8 | 5 | 6.6 |
Derivative liabilities | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, liabilities | (28.5) | (37) | (50.5) | (35.5) |
Total realized/unrealized gains (losses) included in net income, liabilities | 9.8 | (9.1) | 30.3 | (12) |
Total realized/unrealized gains (losses) included in other comprehensive income, liabilities | | 0.4 | 0.5 | 1.6 |
Net purchases, sales, issuances and settlements, liabilities | | | 1 | 0.2 |
Ending balance, liabilities | (18.7) | (45.7) | (18.7) | (45.7) |
Changes in unrealized gains (losses) included in net income relating to positions still held, liabilities | 9.7 | (9.5) | 27.1 | (12.6) |
Gross purchases, sales, issuances and settlements | | | | |
Sales, liabilities | | | 1 | 0.2 |
Net purchases, sales, issuances and settlements, liabilities | | | 1 | 0.2 |
Other liabilities | | | | |
Changes in Level 3 fair value measurements rollforward, assets and liabilities | | | | |
Beginning balance, liabilities | (58.6) | (67.5) | (68.1) | (66.3) |
Total realized/unrealized gains (losses) included in net income, liabilities | (1.6) | 2.8 | (9.5) | 1.6 |
Net purchases, sales, issuances and settlements, liabilities | | | 17.4 | |
Ending balance, liabilities | (60.2) | (64.7) | (60.2) | (64.7) |
Changes in unrealized gains (losses) included in net income relating to positions still held, liabilities | $ (1.6) | $ 2.8 | (7.8) | $ 1.5 |
Gross purchases, sales, issuances and settlements | | | | |
Sales, liabilities | | | 17.4 | |
Net purchases, sales, issuances and settlements, liabilities | | | $ 17.4 | |