Off-Balance Sheet Arrangements, Guarantees and Other Commitments - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Commitments and Contingencies Disclosure [Line Items]
Rent expense for premises and equipment leased under operating leases	$ 24.8	$ 21.9	$ 20.3
Venture capital and private equity fund investments
Commitments and Contingencies Disclosure [Line Items]
Commitments to invest, period from the inception of the fund	10 years
Committed capital call not generally restricted	100.00%
Venture capital and private equity fund investments | Lower Limit
Commitments and Contingencies Disclosure [Line Items]
Expected commitment period to invest in venture capital and private equity funds (in years)	5 years
Venture capital and private equity fund investments | Upper Limit
Commitments and Contingencies Disclosure [Line Items]
Expected commitment period to invest in venture capital and private equity funds (in years)	7 years
Standby Letter of Credit
Commitments and Contingencies Disclosure [Line Items]
Deferred Revenue	$ 10.0	$ 10.0
Collateral in the form of cash	$ 763.0