Contingencies - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014
Commitments and Contingencies Disclosure [Abstract]
Minimum estimated range of aggregate loss for legal proceedings	$ 0
Maximum estimated range of aggregate loss for legal proceedings	33,000,000
Company purchased and holds auction rate securities	94,800,000
Amount of ARS committed to purchase from clients	13,100,000
Eligible investor subject to future buyback potential additional losses related to valuation adjustments	106,100,000
Period of auction rates security to be purchased from rendering of the award	30 days
Loss Contingency Accrual	$ 19,700,000