Fair Value Measurements - Assets and Liabilities Measured on a Recurring Basis (Details) - Recurring $ in Millions	Mar. 31, 2017 USD ($)
Corporate-owned life insurance
Assets
Corporate-owned life insurance	$ 18
Corporate-owned life insurance | Level 1
Assets
Corporate-owned life insurance	0
Corporate-owned life insurance | Level 2
Assets
Corporate-owned life insurance	18
Corporate-owned life insurance | Level 3
Assets
Corporate-owned life insurance	0
Stock fund
Assets
Stuck fund and equity security	38
Stock fund | Level 1
Assets
Stuck fund and equity security	38
Stock fund | Level 2
Assets
Stuck fund and equity security	0
Stock fund | Level 3
Assets
Stuck fund and equity security	0
Equity security
Assets
Stuck fund and equity security	55
Equity security | Level 1
Assets
Stuck fund and equity security	55
Equity security | Level 2
Assets
Stuck fund and equity security	0
Equity security | Level 3
Assets
Stuck fund and equity security	0
Deferred compensation plans
Liabilities
Deferred compensation plans	126
Deferred compensation plans | Level 1
Liabilities
Deferred compensation plans	47
Deferred compensation plans | Level 2
Liabilities
Deferred compensation plans	79
Deferred compensation plans | Level 3
Liabilities
Deferred compensation plans	$ 0