Employee Benefit Plans - Employee Stock Ownership Plan (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Apr. 30, 2007	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Retirement Benefits [Abstract]
ESOP loan	$ 216.8	$ 171.8
ESOP, shares to be purchased	10,453,575
Loan repayments expected annual through 2036	$ 18.8
Cash dividends paid on unallocated ESOP shares		$ 1.1
Minimum age requirement to participate in ESOP		18 years
Minimum work experience within 12 months of hire needed to participate in ESOP		1000 hours
ESOP common stock allocated (in shares)		4,616,996
Unallocated common stock of Employee Stock Ownership Plan (in shares)		5,836,579		5,900,000
Fair value of deferred ESOP shares		$ 64.5
ESOP compensation expense		$ 1.2	$ 1.4