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Fair Value Measurements - Changes in balances of Level 3 financial assets carried at fair value (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |
Financial assets, Beginning Balance | $ 1,762 | $ 1,636 | $ 1,355
Impact of accounting change |  |  | 0
Total realized/unrealized gains (losses) included in Net earnings | (39) | (35) | (31)
Total realized/unrealized gains (losses) included in other comprehensive income (loss) | 17 | 21 | (28)
Purchases and issuances | 1,079 | 347 | 543
Sales and settlements | (437) | (217) | (183)
Transfer into Level 3 | 289 | 139 | 186
Transfer out of Level 3 | (381) | (129) | (160)
Sale of subsidiaries |  |  | (46)
Financial assets, Ending Balance | 2,290 | 1,762 | 1,636
Fixed maturities |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |
Financial assets, Beginning Balance | 1,559 | 1,470 | 1,231
Impact of accounting change |  |  | 0
Total realized/unrealized gains (losses) included in Net earnings | (7) | (14) | (16)
Total realized/unrealized gains (losses) included in other comprehensive income (loss) | 7 | (14) | (19)
Purchases and issuances | 1,032 | 291 | 460
Sales and settlements | (421) | (189) | (183)
Transfer into Level 3 | 289 | 124 | 186
Transfer out of Level 3 | (357) | (109) | (143)
Sale of subsidiaries |  |  | (46)
Financial assets, Ending Balance | 2,102 | 1,559 | 1,470
U.S. government agency |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |
Financial assets, Beginning Balance | 8 | 15 | 15
Impact of accounting change |  |  | 0
Total realized/unrealized gains (losses) included in Net earnings | 0 | (8) | 0
Total realized/unrealized gains (losses) included in other comprehensive income (loss) | 0 | 1 | 0
Purchases and issuances | 0 | 0 | 0
Sales and settlements | 0 | 0 | 0
Transfer into Level 3 | 0 | 0 | 0
Transfer out of Level 3 | 0 | 0 | 0
Sale of subsidiaries |  |  | 0
Financial assets, Ending Balance | 8 | 8 | 15
State and municipal |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |
Financial assets, Beginning Balance | 140 | 89 | 100
Impact of accounting change |  |  | 0
Total realized/unrealized gains (losses) included in Net earnings | 0 | 0 | 0
Total realized/unrealized gains (losses) included in other comprehensive income (loss) | 2 | (4) | (1)
Purchases and issuances | 0 | 57 | 34
Sales and settlements | (2) | (2) | (1)
Transfer into Level 3 | 10 | 0 | 2
Transfer out of Level 3 | (2) | 0 | (39)
Sale of subsidiaries |  |  | (6)
Financial assets, Ending Balance | 148 | 140 | 89
Residential MBS |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |
Financial assets, Beginning Balance | 190 | 224 | 300
Impact of accounting change |  |  | 0
Total realized/unrealized gains (losses) included in Net earnings | (4) | (4) | (11)
Total realized/unrealized gains (losses) included in other comprehensive income (loss) | 2 | (2) | (1)
Purchases and issuances | 1 | 8 | 0
Sales and settlements | (40) | (28) | (34)
Transfer into Level 3 | 44 | 34 | 86
Transfer out of Level 3 | (71) | (42) | (88)
Sale of subsidiaries |  |  | (28)
Financial assets, Ending Balance | 122 | 190 | 224
Commercial MBS |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |
Financial assets, Beginning Balance | 25 | 39 | 44
Impact of accounting change |  |  | 0
Total realized/unrealized gains (losses) included in Net earnings | 2 | (1) | (1)
Total realized/unrealized gains (losses) included in other comprehensive income (loss) | 0 | 0 | (1)
Purchases and issuances | 15 | 0 | 0
Sales and settlements | (10) | (7) | (2)
Transfer into Level 3 | 4 | 0 | 4
Transfer out of Level 3 | 0 | (6) | (1)
Sale of subsidiaries |  |  | (4)
Financial assets, Ending Balance | 36 | 25 | 39
Asset-backed securities |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |
Financial assets, Beginning Balance | 484 | 470 | 226
Impact of accounting change |  |  | 0
Total realized/unrealized gains (losses) included in Net earnings | 0 | (1) | 1
Total realized/unrealized gains (losses) included in other comprehensive income (loss) | 1 | 1 | (7)
Purchases and issuances | 410 | 50 | 265
Sales and settlements | (132) | (52) | (56)
Transfer into Level 3 | 202 | 60 | 53
Transfer out of Level 3 | (221) | (44) | (10)
Sale of subsidiaries |  |  | (2)
Financial assets, Ending Balance | 744 | 484 | 470
Corporate and other |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |
Financial assets, Beginning Balance | 712 | 633 | 546
Impact of accounting change |  |  | 0
Total realized/unrealized gains (losses) included in Net earnings | (5) | 0 | (5)
Total realized/unrealized gains (losses) included in other comprehensive income (loss) | 2 | (10) | (9)
Purchases and issuances | 606 | 176 | 161
Sales and settlements | (237) | (100) | (90)
Transfer into Level 3 | 29 | 30 | 41
Transfer out of Level 3 | (63) | (17) | (5)
Sale of subsidiaries |  |  | (6)
Financial assets, Ending Balance | 1,044 | 712 | 633
Equity securities |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |
Financial assets, Beginning Balance | 174 | 140 | 93
Impact of accounting change |  |  | 0
Total realized/unrealized gains (losses) included in Net earnings | (21) | (12) | (4)
Total realized/unrealized gains (losses) included in other comprehensive income (loss) | 10 | 35 | (9)
Purchases and issuances | 38 | 44 | 77
Sales and settlements | (16) | (28) | 0
Transfer into Level 3 | 0 | 15 | 0
Transfer out of Level 3 | (20) | (20) | (17)
Sale of subsidiaries |  |  | 0
Financial assets, Ending Balance | 165 | 174 | 140
Assets of MIE |  |  |
Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward] |  |  |
Financial assets, Beginning Balance | 29 | 26 | 31
Impact of accounting change |  |  | 0
Total realized/unrealized gains (losses) included in Net earnings | (11) | (9) | (11)
Total realized/unrealized gains (losses) included in other comprehensive income (loss) | 0 | 0 | 0
Purchases and issuances | 9 | 12 | 6
Sales and settlements | 0 | 0 | 0
Transfer into Level 3 | 0 | 0 | 0
Transfer out of Level 3 | (4) | 0 | 0
Sale of subsidiaries |  |  | 0
Financial assets, Ending Balance | $ 23 | $ 29 | $ 26

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