Summary of Significant Accounting Policies (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accounting Policies [Abstract]
Unbilled Audit Premiums	$ 3,000,000	$ 9,000,000	$ 12,000,000
Deposit contracts, liabilities	54,000,000	68,000,000
Depreciation	45,000,000	44,000,000	38,000,000
Goodwill and intangible asset impairment	0
Indefinite-lived Intangible Assets [Line Items]
Interest payments	130,000,000	120,000,000	125,000,000
Income taxes paid	165,000,000	314,000,000	$ 186,000,000
Other Assets
Indefinite-lived Intangible Assets [Line Items]
Intangible assets, net (excluding goodwill)	$ 94,000,000	$ 96,000,000