Acquisition of Radian Asset Assurance Inc. - Assets and Liabilities Assumed (Details) - Radian [Member] $ in Millions	Apr. 01, 2015 USD ($)
Business Acquisition [Line Items]
Cash purchase price	$ 804	[1]
Identifiable assets acquired:
Investments	1,473
Cash	4
Ceded unearned premium reserve, fair value of net assets acquired, before settlement of pre-existing relationships	(3)
Ceded unearned premium reserve, net effect of settlement of pre-existing relationships	(65)
Ceded unearned premium reserve	(68)
Credit derivative assets	30
Deferred tax asset, net, fair value of net assets acquired	263
Deferred tax asset, net, settlement of pre-existing relationships	(56)
Deferred tax asset, net	207
Financial guaranty VIE assets	122
Other assets, fair value of net assets acquired	86
Other assets, settlement of pre-existing relationship	(67)
Other assets	19
Total assets, fair value of net assets acquired	1,975
Total assets, settlement of pre-existing relationships	(188)
Total assets	1,787
Liabilities assumed:
Unearned premium reserves, fair value of net assets acquired	697
Unearned premium reserves, settlement of pre-existing relationships	(216)
Unearned premium reserves	481
Credit derivative liabilities, fair value of net assets acquired	271
Credit derivative liabilities, settlement of pre-existing relationship	(26)
Credit derivative liabilities	245
Financial guaranty VIE liabilities	118
Other liabilities, fair value of net assets acquired	30
Other liabilities, settlement of pre-existing relationship	(49)
Other liabilities	(19)
Total liabilities, fair value of net assets acquired	1,116
Total liabilities, settlement of pre-existing relationships	(291)
Total liabilities	825
Net assets resulting from acquisition, fair value of net assets acquired	859
Net assets resulting from acquisition, settlement of pre-existing relationships	103
Net asset effect of Radian Asset Acquisition	962
Bargain purchase gain and settlement of pre-existing relationships resulting from Radian Asset Acquisition, after tax, fair value of net assets acquired	55
Bargain purchase gain and settlement of pre-existing relationships resulting from Radian Asset Acquisition, after-tax, settlement of pre-existing relationships	103
Bargain purchase gain and settlement of pre-existing relationships resulting from Radian Asset Acquisition, after-tax	158
Deferred tax, settlement of pre-existing relationships	56
Deferred tax	56
Bargain purchase gain and settlement of pre-existing relationships resulting from Radian Asset Acquisitions, pre-tax, fair value of net assets acquired	55
Bargain purchase gain and settlement of pre-existing relationships resulting from Radian Asset Acquisition, pre-tax, settlement of pre-existing relationships	159
Bargain purchase gain and settlement of pre-existing relationships resulting from Radian Asset Acquisition, pre-tax	214
Consideration transferred	987
Assumed assets including pre-existing relationship	1,042
Settlement of pre-existing relationship	$ (183)

[1] The cash purchase price of $804 million was the cash transferred for the acquisition which was allocated as follows: (1) $987 million for the purchase of net assets of $1,042 million, and (2) the settlement of pre-existing relationships between Radian and Assured Guaranty at a fair value of $(183) million.