Loans - Summary of Delinquent and Nonaccrual Loans (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Accounts Notes And Loans Receivable [Line Items]
Total Past Due and Nonaccrual	$ 19,835	$ 13,546
90 Days or More Past Due and Still Accruing	2,814	2,109
Nonaccrual Past Due and Still Accruing	11,240	11,359
Current	4,421,053	3,641,716
Total loans	$ 4,440,888	$ 3,655,262
Percentage of Total Loans Due 30-59 Days	0.13%	0.00%
Percentage of Total Loans Due 90 Days or More	0.07%	0.06%
Percentage of Total Loans Due Nonaccrual	0.25%	0.31%
Percentage of Total Loans	0.45%	0.37%
Residential Properties
Accounts Notes And Loans Receivable [Line Items]
Total loans	$ 3,086,158	$ 2,581,245
Commercial Real Estate
Accounts Notes And Loans Receivable [Line Items]
Total loans	841,923	696,748
Commercial and Industrial Loans
Accounts Notes And Loans Receivable [Line Items]
Total Past Due and Nonaccrual	11,245	10,406
90 Days or More Past Due and Still Accruing	50	789
Nonaccrual Past Due and Still Accruing	8,923	9,617
Current	399,625	300,373
Total loans	410,870	310,779
Consumer Loans
Accounts Notes And Loans Receivable [Line Items]
Total Past Due and Nonaccrual	7
Current	23,464	29,330
Total loans	23,471	29,330
Land
Accounts Notes And Loans Receivable [Line Items]
Total loans	78,466	37,160
30-59 Days
Accounts Notes And Loans Receivable [Line Items]
Total Past Due and Nonaccrual	5,661	78
30-59 Days | Commercial and Industrial Loans
Accounts Notes And Loans Receivable [Line Items]
Total Past Due and Nonaccrual	2,159
60-89 Days
Accounts Notes And Loans Receivable [Line Items]
Total Past Due and Nonaccrual	120
60-89 Days | Commercial and Industrial Loans
Accounts Notes And Loans Receivable [Line Items]
Total Past Due and Nonaccrual	113
60-89 Days | Consumer Loans
Accounts Notes And Loans Receivable [Line Items]
Total Past Due and Nonaccrual	7
Real Estate Loans
Accounts Notes And Loans Receivable [Line Items]
Total loans	4,006,547	3,315,153
Real Estate Loans | Residential Properties
Accounts Notes And Loans Receivable [Line Items]
Total Past Due and Nonaccrual	5,518	78
90 Days or More Past Due and Still Accruing	1,461
Nonaccrual Past Due and Still Accruing	675
Current	3,080,640	2,581,167
Total loans	3,086,158	2,581,245
Real Estate Loans | Commercial Real Estate
Accounts Notes And Loans Receivable [Line Items]
Total Past Due and Nonaccrual	3,065	3,062
90 Days or More Past Due and Still Accruing	1,303	1,320
Nonaccrual Past Due and Still Accruing	1,642	1,742
Current	838,858	693,686
Total loans	841,923	696,748
Real Estate Loans | Land
Accounts Notes And Loans Receivable [Line Items]
Current	78,466	37,160
Total loans	78,466	37,160
Real Estate Loans | 30-59 Days | Residential Properties
Accounts Notes And Loans Receivable [Line Items]
Total Past Due and Nonaccrual	3,382	$ 78
Real Estate Loans | 30-59 Days | Commercial Real Estate
Accounts Notes And Loans Receivable [Line Items]
Total Past Due and Nonaccrual	$ 120