Commitments and Contingencies - Narrative (Details) AUD in Millions, $ in Millions	1 Months Ended		12 Months Ended
	Apr. 30, 2013 AUD investment	Dec. 31, 2003 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Aug. 03, 2015 employee shareholder
Loss Contingencies [Line Items]
Sale of equity investment in Rock-McGraw, Inc., percentage		45.00%
Proceeds from the disposition of equity investment in Rock-McGraw		$ 382
Pre-tax gain from Sale of equity investment in Rock-McGraw		131
After-tax gain from Sale of equity investment in Rock-McGraw		58
Pre-tax gain pursuant to sale-leaseback accounting rules		212
After-tax gain pursuant to sale-leaseback accounting rules		$ 126
Deferred gain					$ 60
Gain amortized during year			$ 4	$ 21	$ 15
Shareholder Derivative Action [Member]
Loss Contingencies [Line Items]
Number of shareholders commencing punitive derivative action | shareholder						2
Number of former employees named as defendants | employee						3
City of Swan [Member]
Loss Contingencies [Line Items]
Alleged losses related to synthetic collateralized debt obligations, number of investments | investment	8
Damages sought | AUD	AUD 327