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Segment Reporting - Segment Results and Reconciliations to GAAP (Detail) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2019 | Jun. 30, 2018 | Jun. 30, 2019 | Jun. 30, 2018
Interest income: |  |  |  |
Cash and investments | $ 25 | $ 24 | $ 52 | $ 41
Total interest income | 1,204 | 1,227 | 2,439 | 2,399
Total interest expense | 911 | 929 | 1,860 | 1,773
Net interest income | 293 | 298 | 579 | 626
Less: provisions for loan losses | 68 | 112 | 144 | 199
Net interest income after provisions for loan losses | 225 | 186 | 435 | 427
Other income (loss): |  |  |  |
Servicing revenue | 60 | 71 | 122 | 140
Asset recovery and business processing revenue | 123 | 99 | 242 | 207
Other income (loss) | (21) | (27) | 2 | 9
Gains on sales of loans | 16 |  | 16 |
Gains (losses) on debt repurchases | 44 | (7) | 59 | (8)
Total other income | 222 | 136 | 441 | 348
Expenses: |  |  |  |
Direct operating expenses | 179 | 129 | 363 | 323
Unallocated shared services expenses | 62 | 72 | 134 | 153
Total operating expenses | 241 | 201 | 497 | 476
Goodwill and acquired intangible asset impairment and amortization | 11 | 6 | 18 | 16
Restructuring/other reorganization expenses | 1 | 2 | 2 | 9
Total expenses | 253 | 209 | 517 | 501
Income before income tax expense | 194 | 113 | 359 | 274
Income tax expense (benefit) | 41 | 30 | 78 | 64
Net income (loss) | 153 | 83 | 281 | 210
Education Loan Portfolio [Member] |  |  |  |
Interest income: |  |  |  |
Total interest income | 1,178 | 1,202 | 2,385 | 2,356
Other Loans [Member] |  |  |  |
Interest income: |  |  |  |
Total interest income | 1 | 1 | 2 | 2
Operating Segments [Member] |  |  |  |
Interest income: |  |  |  |
Cash and investments | 25 | 24 | 52 | 41
Total interest income | 1,220 | 1,242 | 2,470 | 2,423
Total interest expense | 924 | 923 | 1,874 | 1,774
Net interest income | 296 | 319 | 596 | 649
Less: provisions for loan losses | 68 | 112 | 144 | 199
Net interest income after provisions for loan losses | 228 | 207 | 452 | 450
Other income (loss): |  |  |  |
Servicing revenue | 60 | 71 | 122 | 140
Asset recovery and business processing revenue | 123 | 99 | 242 | 207
Other income (loss) | 11 | 3 | 25 | 6
Gains on sales of loans | 16 |  | 16 |
Gains (losses) on debt repurchases | 32 | (7) | 47 | (8)
Total other income | 242 | 166 | 452 | 345
Expenses: |  |  |  |
Direct operating expenses | 179 | 129 | 363 | 323
Unallocated shared services expenses | 62 | 72 | 134 | 153
Total operating expenses | 241 | 201 | 497 | 476
Restructuring/other reorganization expenses | 1 | 2 | 2 | 9
Total expenses | 242 | 203 | 499 | 485
Income before income tax expense | 228 | 170 | 405 | 310
Income tax expense (benefit) | 53 | 39 | 93 | 72
Net income (loss) | 175 | 131 | 312 | 238
Operating Segments [Member] | Federal Education Loans [Member] |  |  |  |
Interest income: |  |  |  |
Cash and investments | 14 | 12 | 30 | 19
Total interest income | 772 | 788 | 1,568 | 1,528
Total interest expense | 627 | 622 | 1,278 | 1,193
Net interest income | 145 | 166 | 290 | 335
Less: provisions for loan losses | 8 | 40 | 15 | 50
Net interest income after provisions for loan losses | 137 | 126 | 275 | 285
Other income (loss): |  |  |  |
Servicing revenue | 57 | 68 | 117 | 134
Asset recovery and business processing revenue | 58 | 34 | 108 | 70
Other income (loss) | 7 |  | 15 | 1
Total other income | 122 | 102 | 240 | 205
Expenses: |  |  |  |
Direct operating expenses | 89 | 36 | 180 | 115
Total operating expenses | 89 | 36 | 180 | 115
Total expenses | 89 | 36 | 180 | 115
Income before income tax expense | 170 | 192 | 335 | 375
Income tax expense (benefit) | 39 | 44 | 77 | 86
Net income (loss) | 131 | 148 | 258 | 289
Operating Segments [Member] | Consumer Lending [Member] |  |  |  |
Interest income: |  |  |  |
Cash and investments | 4 | 3 | 9 | 6
Total interest income | 441 | 445 | 889 | 879
Total interest expense | 255 | 252 | 516 | 490
Net interest income | 186 | 193 | 373 | 389
Less: provisions for loan losses | 60 | 72 | 129 | 149
Net interest income after provisions for loan losses | 126 | 121 | 244 | 240
Other income (loss): |  |  |  |
Servicing revenue | 3 | 3 | 5 | 6
Other income (loss) |  |  | 1 |
Gains on sales of loans | 16 |  | 16 |
Total other income | 19 | 3 | 22 | 6
Expenses: |  |  |  |
Direct operating expenses | 34 | 39 | 72 | 95
Total operating expenses | 34 | 39 | 72 | 95
Total expenses | 34 | 39 | 72 | 95
Income before income tax expense | 111 | 85 | 194 | 151
Income tax expense (benefit) | 26 | 19 | 44 | 35
Net income (loss) | 85 | 66 | 150 | 116
Operating Segments [Member] | Business Processing [Member] |  |  |  |
Other income (loss): |  |  |  |
Asset recovery and business processing revenue | 65 | 65 | 134 | 137
Total other income | 65 | 65 | 134 | 137
Expenses: |  |  |  |
Direct operating expenses | 56 | 54 | 111 | 113
Total operating expenses | 56 | 54 | 111 | 113
Total expenses | 56 | 54 | 111 | 113
Income before income tax expense | 9 | 11 | 23 | 24
Income tax expense (benefit) | 2 | 3 | 6 | 6
Net income (loss) | 7 | 8 | 17 | 18
Operating Segments [Member] | Other Segment [Member] |  |  |  |
Interest income: |  |  |  |
Cash and investments | 7 | 9 | 13 | 16
Total interest income | 7 | 9 | 13 | 16
Total interest expense | 42 | 49 | 80 | 91
Net interest income | (35) | (40) | (67) | (75)
Net interest income after provisions for loan losses | (35) | (40) | (67) | (75)
Other income (loss): |  |  |  |
Other income (loss) | 4 | 3 | 9 | 5
Gains (losses) on debt repurchases | 32 | (7) | 47 | (8)
Total other income | 36 | (4) | 56 | (3)
Expenses: |  |  |  |
Unallocated shared services expenses | 62 | 72 | 134 | 153
Total operating expenses | 62 | 72 | 134 | 153
Restructuring/other reorganization expenses | 1 | 2 | 2 | 9
Total expenses | 63 | 74 | 136 | 162
Income before income tax expense | (62) | (118) | (147) | (240)
Income tax expense (benefit) | (14) | (27) | (34) | (55)
Net income (loss) | (48) | (91) | (113) | (185)
Operating Segments [Member] | Education Loan Portfolio [Member] |  |  |  |
Interest income: |  |  |  |
Total interest income | 1,194 | 1,217 | 2,416 | 2,380
Operating Segments [Member] | Education Loan Portfolio [Member] | Federal Education Loans [Member] |  |  |  |
Interest income: |  |  |  |
Total interest income | 758 | 775 | 1,537 | 1,507
Operating Segments [Member] | Education Loan Portfolio [Member] | Consumer Lending [Member] |  |  |  |
Interest income: |  |  |  |
Total interest income | 436 | 442 | 879 | 873
Operating Segments [Member] | Other Loans [Member] |  |  |  |
Interest income: |  |  |  |
Total interest income | 1 | 1 | 2 | 2
Operating Segments [Member] | Other Loans [Member] | Federal Education Loans [Member] |  |  |  |
Interest income: |  |  |  |
Total interest income |  | 1 | 1 | 2
Operating Segments [Member] | Other Loans [Member] | Consumer Lending [Member] |  |  |  |
Interest income: |  |  |  |
Total interest income | 1 |  | 1 |
Adjustments [Member] | Reclassifications [Member] |  |  |  |
Interest income: |  |  |  |
Total interest income | 1 | 3 | 2 | 11
Total interest expense | (2) | 10 | 2 | 4
Net interest income | 3 | (7) |  | 7
Net interest income after provisions for loan losses | 3 | (7) |  | 7
Other income (loss): |  |  |  |
Other income (loss) | (38) | 7 | (39) | (7)
Gains (losses) on debt repurchases | 35 |  | 39 |
Total other income | (3) | 7 |  | (7)
Adjustments [Member] | Additions (Subtractions) [Member] |  |  |  |
Interest income: |  |  |  |
Total interest income | (17) | (18) | (33) | (35)
Total interest expense | (11) | (4) | (16) | (5)
Net interest income | (6) | (14) | (17) | (30)
Net interest income after provisions for loan losses | (6) | (14) | (17) | (30)
Other income (loss): |  |  |  |
Other income (loss) | 6 | (37) | 16 | 10
Gains (losses) on debt repurchases | (23) |  | (27) |
Total other income | (17) | (37) | (11) | 10
Expenses: |  |  |  |
Goodwill and acquired intangible asset impairment and amortization | 11 | 6 | 18 | 16
Total expenses | 11 | 6 | 18 | 16
Income before income tax expense | (34) | (57) | (46) | (36)
Income tax expense (benefit) | (12) | (9) | (15) | (8)
Net income (loss) | (22) | (48) | (31) | (28)
Adjustments [Member] | Total Adjustments [Member] |  |  |  |
Interest income: |  |  |  |
Total interest income | (16) | (15) | (31) | (24)
Total interest expense | (13) | 6 | (14) | (1)
Net interest income | (3) | (21) | (17) | (23)
Net interest income after provisions for loan losses | (3) | (21) | (17) | (23)
Other income (loss): |  |  |  |
Other income (loss) | (32) | (30) | (23) | 3
Gains (losses) on debt repurchases | 12 |  | 12 |
Total other income | (20) | (30) | (11) | 3
Expenses: |  |  |  |
Goodwill and acquired intangible asset impairment and amortization | 11 | 6 | 18 | 16
Total expenses | 11 | 6 | 18 | 16
Income before income tax expense | (34) | (57) | (46) | (36)
Income tax expense (benefit) | (12) | (9) | (15) | (8)
Net income (loss) | (22) | (48) | (31) | (28)
Adjustments [Member] | Education Loan Portfolio [Member] | Reclassifications [Member] |  |  |  |
Interest income: |  |  |  |
Total interest income | 1 | 3 | 2 | 11
Adjustments [Member] | Education Loan Portfolio [Member] | Additions (Subtractions) [Member] |  |  |  |
Interest income: |  |  |  |
Total interest income | (17) | (18) | (33) | (35)
Adjustments [Member] | Education Loan Portfolio [Member] | Total Adjustments [Member] |  |  |  |
Interest income: |  |  |  |
Total interest income | $ (16) | $ (15) | $ (31) | $ (24)

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