Commitments and Contingent Liabilities - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Future Minimum Lease Payments Due	$ 189.6
Future Minimum Lease Payments Due Within Twelve Months	50.8
Future Minimum Lease Payments Due Within Two Years	25.8
Future Minimum Lease Payments Due Within Three Years	22.5
Future Minimum Lease Payments Due Within Four Years	18.0
Future Minimum Lease Payments Due Within Five Years	13.9
Future Minimum Lease Payments Due Thereafter	58.6
Rental Expense	51.4	$ 42.5	$ 44.2
Total Unfunded Commitments	314.0
Pending Litigation | Unfavorable Regulatory Action | Minimum
Loss Contingencies
Loss Contingency, Estimate of Possible Loss	12.0
Pending Litigation | Unfavorable Regulatory Action | Maximum
Loss Contingencies
Loss Contingency, Estimate of Possible Loss	$ 15.0