v3.8.0.1
Condensed Financial Information of Registrant - Condensed Statements Of Cash Flows (Details) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Net cash provided by operating activities $ 1,489 $ 1,851 $ 658
Cash flows from investing activities:      
Purchases of investments (2,704) (2,450) (1,321)
Sales and maturities of investments 1,899 1,656 669
Investments in acquisitions (50) (1,297) (18)
Other investing activities, net 12 0 7
Net cash used in investing activities (1,265) (2,397) (813)
Cash flows from financing activities:      
Proceeds from borrowings 1,400 8,946 1,925
Payment of long-term debt (1,353) (6,076) (1,583)
Common stock repurchases (65) (63) (53)
Debt issue costs (3) (76) (4)
Purchase of noncontrolling interest (66) (14) 0
Other financing activities, net 5 0 20
Net cash (used in) provided by financing activities (82) 2,717 305
Net increase in cash and cash equivalents 142 2,170 150
Cash and cash equivalents, beginning of period 3,930 1,760 1,610
Cash and cash equivalents, end of period 4,072 3,930 1,760
Parent Company      
Dividends from subsidiaries, return on investment 292 25 11
Other operating activities, net (132) (71) (29)
Net cash provided by operating activities 160 (46) (18)
Cash flows from investing activities:      
Capital contributions to subsidiaries (339) (691) (646)
Purchases of investments (38) (112) (17)
Sales and maturities of investments 4 169 9
Dividends from subsidiaries, return of investment 28 100 3
Investments in acquisitions (59) (2,248) (113)
Intercompany activities (322) 575 (463)
Other investing activities, net (1) 0 7
Net cash used in investing activities (83) (3,357) (294)
Cash flows from financing activities:      
Proceeds from borrowings 1,400 8,934 1,925
Payment of long-term debt (1,350) (5,377) (1,575)
Common stock repurchases (65) (63) (53)
Debt issue costs 0 (76) (4)
Purchase of noncontrolling interest (66) (14) 0
Other financing activities, net 5 0 20
Net cash (used in) provided by financing activities (76) 3,404 313
Net increase in cash and cash equivalents 1 1 1
Cash and cash equivalents, beginning of period 5 4 3
Cash and cash equivalents, end of period $ 6 $ 5 $ 4