Valuation Techniques, Significant Unobservable Inputs, and Quantitative Information (Detail) - Fair Value, Measurements, Recurring - Fair Value, Inputs, Level 3 - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Auction Rate
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Assets, fair value	$ 4.7	$ 17.1
Auction Rate | Group One
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Valuation Technique	Comparables	Discounted Cash Flow
Unobservable Inputs	Price	Remaining Lives
Auction Rate | Group Two
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unobservable Inputs		Discount Rates
Auction Rate | Lower Limit
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial instrument price (in dollars per share)	$ 84
Financial instrument remaining lives		5 months 1 day
Financial instrument discount rate		0.30%
Auction Rate | Upper Limit
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial instrument price (in dollars per share)	$ 99
Financial instrument remaining lives		8 years 7 months 20 days
Financial instrument discount rate		4.40%
Visa Conversion Rate Swap
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial liabilities, fair value	$ 25.2	$ 10.8
Visa Conversion Rate Swap | Group One
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Valuation Technique	Discounted Cash Flow	Discounted Cash Flow
Unobservable Inputs	Visa Class A Appreciation	Visa Class A Appreciation
Visa Conversion Rate Swap | Group Two
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unobservable Inputs	Conversion Rate	Conversion Rate
Visa Conversion Rate Swap | Group Three
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unobservable Inputs	Expected Duration	Expected Duration
Visa Conversion Rate Swap | Lower Limit
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial instrument appreciation rate	7.00%	9.50%
Financial instruments conversion rate	163.00%	161.00%
Financial instrument, expected duration	1 year 6 months	1 year 6 months
Visa Conversion Rate Swap | Upper Limit
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial instrument appreciation rate	11.00%	15.00%
Financial instruments conversion rate	165.00%	165.00%
Financial instrument, expected duration	4 years 6 months	4 years 6 months