Deposits - Composition of Deposits and Interest Expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Deposits And Borrowings Maturities [Line Items]
Balance	$ 5,272,377	$ 4,876,611	$ 3,908,842
Interest Expense	19,692	12,944	10,128
Noninterest-bearing demand
Schedule Of Deposits And Borrowings Maturities [Line Items]
Balance	1,263,833	1,227,766	1,083,919
Interest-bearing demand
Schedule Of Deposits And Borrowings Maturities [Line Items]
Balance	638,300	616,188	335,099
Interest Expense	111	818	19
Money market
Schedule Of Deposits And Borrowings Maturities [Line Items]
Balance	936,461	605,184	376,612
Interest Expense	4,199	1,299	572
Savings
Schedule Of Deposits And Borrowings Maturities [Line Items]
Balance	1,050,131	1,061,265	1,027,095
Interest Expense	2,002	1,712	1,607
Certificates of deposit
Schedule Of Deposits And Borrowings Maturities [Line Items]
Balance	1,383,652	1,366,208	1,086,117
Interest Expense	$ 13,380	$ 9,115	$ 7,930