Deposits - Deposits by Category, Including Summary of Remaining Time to Maturity for Time Deposits (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Money market and demand:
Noninterest-bearing demand	$ 1,420,760	$ 1,266,306
Interest-bearing demand	1,071,512	935,333
Money market	1,347,146	1,257,520
Total money market and demand	3,839,418	3,459,159
Savings	549,744	547,293
Customer certificates of deposit by maturity:
Less than one year	167,757	192,320
One year to two years	103,192	74,165
Two years to three years	46,827	32,687
Three years to four years	5,962	24,919
Over four years	6,399	8,533
Total customer time certificates	330,137	332,624
Jumbo certificates of deposit, by maturity:
Less than one year	166,348	174,981
One year to two years	94,905	43,037
Two years to three years	30,400	20,655
Three years to four years	3,512	17,005
Over four years	3,769	4,882
Total jumbo certificates of deposit	298,934	260,560
Total customer deposits	5,018,233	4,599,636
Brokered deposits less than one year	229,371	138,802
Total deposits	5,247,604	4,738,438
Domestic
Jumbo certificates of deposit, by maturity:
Total jumbo certificates of deposit	$ 298,934	$ 260,560