Valuation Techniques, Significant Unobservable Inputs, and Quantitative Information (Detail) (Fair Value, Inputs, Level 3, Auction Rate Securities, USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial instrument, fair value	17.5
Group One
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Valuation Technique	Discounted Cash Flow
Unobservable Inputs	Remaining lives
Group Two
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Valuation Technique	Discounted Cash Flow
Unobservable Inputs	Discount rates
Lower Limit
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial instrument remaining lives	1 year 2 months 12 days
Financial instrument discount rate	0.10%
Upper Limit
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Financial instrument remaining lives	8 years 7 months 6 days
Financial instrument discount rate	8.40%