Allowance for Loan Losses - Summary of Loans Based on Method for Determining Allowance (Detail) - USD ($) $ in Thousands | Mar. 31, 2018 | Dec. 31, 2017 | Jun. 30, 2017 | Mar. 31, 2017 | Jun. 30, 2016 |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | $ 8,704,392 | $ 7,977,784 | | | |
Allowance for loan losses | 49,213 | 47,145 | $ 47,145 | $ 39,431 | $ 37,897 |
New Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 7,976,251 | 7,661,385 | | | |
Allowance for loan losses | 44,690 | | | 35,362 | |
Acquired Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 728,141 | 316,399 | | | |
Allowance for loan losses | 1,113 | | | 1,344 | |
Unallocated Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, Individually evaluated for impairment | 0 | | | | |
Loans - Recorded investment, Collectively evaluated for impairment | 8,704,392 | 7,977,784 | | | |
Allowance for credit loss, Individually evaluated for impairment | 0 | | | | |
Allowance for credit loss, Collectively evaluated for impairment | 1,500 | 1,500 | | | |
Allowance for loan losses | 1,500 | | | | |
Total real estate loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 6,908,251 | 6,318,053 | | | |
Total real estate loans | New Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, Individually evaluated for impairment | 653 | 1,226 | | | |
Loans - Recorded investment, Collectively evaluated for impairment | 6,269,227 | 6,019,803 | | | |
Loans - Recorded investment, ASC 310-30 loans | 6,269,880 | 6,021,029 | | | |
Allowance for credit loss, Individually evaluated for impairment | 66 | 66 | | | |
Allowance for credit loss, Collectively evaluated for impairment | 27,855 | 27,736 | | | |
Total real estate loans | Acquired Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, Individually evaluated for impairment | 4,609 | 4,655 | | | |
Loans - Recorded investment, Collectively evaluated for impairment | 428,255 | 147,354 | | | |
Allowance for credit loss, Individually evaluated for impairment | 129 | 129 | | | |
Allowance for credit loss, Collectively evaluated for impairment | 653 | 683 | | | |
Commercial real estate | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 2,418,753 | 2,245,859 | | | |
Allowance for loan losses | 14,197 | | 13,870 | 9,964 | 10,123 |
Commercial real estate | New Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, Individually evaluated for impairment | 0 | 0 | | | |
Loans - Recorded investment, Collectively evaluated for impairment | 2,168,606 | 2,103,788 | | | |
Loans - Recorded investment, ASC 310-30 loans | 2,168,606 | 2,103,788 | | | |
Allowance for credit loss, Individually evaluated for impairment | 0 | 0 | | | |
Allowance for credit loss, Collectively evaluated for impairment | 12,381 | 12,084 | | | |
Allowance for loan losses | 12,381 | | | 8,703 | |
Commercial real estate | Acquired Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, Individually evaluated for impairment | 3,847 | 3,893 | | | |
Loans - Recorded investment, Collectively evaluated for impairment | 107,447 | 33,843 | | | |
Allowance for credit loss, Individually evaluated for impairment | 129 | 129 | | | |
Allowance for credit loss, Collectively evaluated for impairment | 234 | 209 | | | |
Allowance for loan losses | 337 | | | 344 | |
Commercial real estate | Unallocated Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Allowance for loan losses | 0 | | | | |
Owner-occupied commercial real estate | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 1,156,610 | 1,003,881 | | | |
Allowance for loan losses | 3,778 | | 3,365 | 2,711 | 2,597 |
Owner-occupied commercial real estate | New Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, Individually evaluated for impairment | 0 | 0 | | | |
Loans - Recorded investment, Collectively evaluated for impairment | 1,074,076 | 987,781 | | | |
Loans - Recorded investment, ASC 310-30 loans | 1,074,076 | 987,781 | | | |
Allowance for credit loss, Individually evaluated for impairment | 0 | 0 | | | |
Allowance for credit loss, Collectively evaluated for impairment | 3,720 | 3,310 | | | |
Allowance for loan losses | 3,720 | | | 2,650 | |
Owner-occupied commercial real estate | Acquired Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, Individually evaluated for impairment | 0 | 0 | | | |
Loans - Recorded investment, Collectively evaluated for impairment | 82,534 | 16,100 | | | |
Allowance for credit loss, Individually evaluated for impairment | 0 | 0 | | | |
Allowance for credit loss, Collectively evaluated for impairment | 66 | 55 | | | |
Allowance for loan losses | 58 | | | 61 | |
Owner-occupied commercial real estate | Unallocated Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Allowance for loan losses | 0 | | | | |
1-4 single family residential | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 2,432,243 | 2,270,570 | | | |
Allowance for loan losses | 7,493 | | 7,978 | 7,913 | 7,379 |
1-4 single family residential | New Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, Individually evaluated for impairment | 524 | 1,096 | | | |
Loans - Recorded investment, Collectively evaluated for impairment | 2,232,267 | 2,184,266 | | | |
Loans - Recorded investment, ASC 310-30 loans | 2,232,791 | 2,185,362 | | | |
Allowance for credit loss, Individually evaluated for impairment | 0 | 0 | | | |
Allowance for credit loss, Collectively evaluated for impairment | 7,281 | 7,769 | | | |
Allowance for loan losses | 7,281 | | | 7,639 | |
1-4 single family residential | Acquired Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, Individually evaluated for impairment | 267 | 267 | | | |
Loans - Recorded investment, Collectively evaluated for impairment | 163,921 | 57,428 | | | |
Allowance for credit loss, Individually evaluated for impairment | 0 | 0 | | | |
Allowance for credit loss, Collectively evaluated for impairment | 104 | 184 | | | |
Allowance for loan losses | 172 | | | 243 | |
1-4 single family residential | Unallocated Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Allowance for loan losses | 0 | | | | |
Construction, land and development | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 796,152 | 703,518 | | | |
Allowance for loan losses | 4,288 | | 4,345 | 4,918 | 4,677 |
Construction, land and development | New Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, Individually evaluated for impairment | 0 | 0 | | | |
Loans - Recorded investment, Collectively evaluated for impairment | 732,551 | 684,462 | | | |
Loans - Recorded investment, ASC 310-30 loans | 732,551 | 684,462 | | | |
Allowance for credit loss, Individually evaluated for impairment | 0 | 0 | | | |
Allowance for credit loss, Collectively evaluated for impairment | 4,109 | 4,164 | | | |
Allowance for loan losses | 4,109 | | | 4,569 | |
Construction, land and development | Acquired Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, Individually evaluated for impairment | 0 | 0 | | | |
Loans - Recorded investment, Collectively evaluated for impairment | 32,413 | 5,889 | | | |
Allowance for credit loss, Individually evaluated for impairment | 0 | 0 | | | |
Allowance for credit loss, Collectively evaluated for impairment | 39 | 36 | | | |
Allowance for loan losses | 36 | | | 44 | |
Construction, land and development | Unallocated Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Allowance for loan losses | 0 | | | | |
Home equity loans and lines of credit | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 104,493 | 94,225 | | | |
Allowance for loan losses | 616 | | 674 | 726 | 648 |
Home equity loans and lines of credit | New Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, Individually evaluated for impairment | 129 | 130 | | | |
Loans - Recorded investment, Collectively evaluated for impairment | 61,727 | 59,506 | | | |
Loans - Recorded investment, ASC 310-30 loans | 61,856 | 59,636 | | | |
Allowance for credit loss, Individually evaluated for impairment | 66 | 66 | | | |
Allowance for credit loss, Collectively evaluated for impairment | 364 | 409 | | | |
Allowance for loan losses | 430 | | | 450 | |
Home equity loans and lines of credit | Acquired Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, Individually evaluated for impairment | 495 | 495 | | | |
Loans - Recorded investment, Collectively evaluated for impairment | 41,940 | 34,094 | | | |
Allowance for credit loss, Individually evaluated for impairment | 0 | 0 | | | |
Allowance for credit loss, Collectively evaluated for impairment | 210 | 199 | | | |
Allowance for loan losses | 186 | | | 276 | |
Home equity loans and lines of credit | Unallocated Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Allowance for loan losses | 0 | | | | |
Total other loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 1,796,141 | 1,659,731 | | | |
Total other loans | New Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, Individually evaluated for impairment | 0 | 0 | | | |
Loans - Recorded investment, Collectively evaluated for impairment | 1,706,371 | 1,640,356 | | | |
Loans - Recorded investment, ASC 310-30 loans | 1,706,371 | 1,640,356 | | | |
Allowance for credit loss, Individually evaluated for impairment | 0 | 0 | | | |
Allowance for credit loss, Collectively evaluated for impairment | 16,769 | 14,823 | | | |
Total other loans | Acquired Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, Individually evaluated for impairment | 272 | 272 | | | |
Loans - Recorded investment, Collectively evaluated for impairment | 65,691 | 5,049 | | | |
Allowance for credit loss, Individually evaluated for impairment | 272 | 272 | | | |
Allowance for credit loss, Collectively evaluated for impairment | 59 | 47 | | | |
Commercial and industrial | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 1,771,845 | 1,652,065 | | | |
Allowance for loan losses | 17,114 | | 15,141 | 12,953 | 12,245 |
Commercial and industrial | New Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, Individually evaluated for impairment | 0 | 0 | | | |
Loans - Recorded investment, Collectively evaluated for impairment | 1,701,651 | 1,634,372 | | | |
Loans - Recorded investment, ASC 310-30 loans | 1,701,651 | 1,634,372 | | | |
Allowance for credit loss, Individually evaluated for impairment | 0 | 0 | | | |
Allowance for credit loss, Collectively evaluated for impairment | 16,681 | 14,702 | | | |
Allowance for loan losses | 16,681 | | | 11,273 | |
Commercial and industrial | Acquired Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, Individually evaluated for impairment | 272 | 272 | | | |
Loans - Recorded investment, Collectively evaluated for impairment | 47,488 | 4,790 | | | |
Allowance for credit loss, Individually evaluated for impairment | 272 | 272 | | | |
Allowance for credit loss, Collectively evaluated for impairment | 56 | 41 | | | |
Allowance for loan losses | 321 | | | 370 | |
Commercial and industrial | Unallocated Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Allowance for loan losses | 0 | | | | |
Consumer | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 24,296 | 7,666 | | | |
Allowance for loan losses | 227 | | $ 272 | 246 | $ 228 |
Consumer | New Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, Individually evaluated for impairment | 0 | 0 | | | |
Loans - Recorded investment, Collectively evaluated for impairment | 4,720 | 5,984 | | | |
Loans - Recorded investment, ASC 310-30 loans | 4,720 | 5,984 | | | |
Allowance for credit loss, Individually evaluated for impairment | 0 | 0 | | | |
Allowance for credit loss, Collectively evaluated for impairment | 88 | 121 | | | |
Allowance for loan losses | 88 | | | 78 | |
Consumer | Acquired Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, Individually evaluated for impairment | 0 | 0 | | | |
Loans - Recorded investment, Collectively evaluated for impairment | 18,203 | 259 | | | |
Allowance for credit loss, Individually evaluated for impairment | 0 | 0 | | | |
Allowance for credit loss, Collectively evaluated for impairment | 3 | 6 | | | |
Allowance for loan losses | 3 | | | 6 | |
Consumer | Unallocated Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Allowance for loan losses | 0 | | | | |
ASC 310-30 Loans | Acquired Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 229,314 | 159,069 | | | |
Allowance for loan losses | 1,910 | | | 2,725 | |
ASC 310-30 Loans | Unallocated Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 0 | | | | |
Allowance for loan losses | 0 | | | | |
ASC 310-30 Loans | Total real estate loans | New Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 0 | 0 | | | |
Allowance for loan losses | 0 | 0 | | | |
ASC 310-30 Loans | Total real estate loans | Acquired Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 205,507 | 145,015 | | | |
Allowance for loan losses | 1,662 | 1,618 | | | |
ASC 310-30 Loans | Commercial real estate | New Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 0 | 0 | | | |
Allowance for loan losses | 0 | 0 | | | |
ASC 310-30 Loans | Commercial real estate | Acquired Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 138,853 | 104,335 | | | |
Allowance for loan losses | 1,479 | 1,448 | | 917 | |
ASC 310-30 Loans | Owner-occupied commercial real estate | New Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 0 | 0 | | | |
Allowance for loan losses | 0 | 0 | | | |
ASC 310-30 Loans | Owner-occupied commercial real estate | Acquired Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 0 | 0 | | | |
Allowance for loan losses | 0 | 0 | | 0 | |
ASC 310-30 Loans | 1-4 single family residential | New Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 0 | 0 | | | |
Allowance for loan losses | 0 | 0 | | | |
ASC 310-30 Loans | 1-4 single family residential | Acquired Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 35,264 | 27,513 | | | |
Allowance for loan losses | 40 | 25 | | 31 | |
ASC 310-30 Loans | Construction, land and development | New Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 0 | 0 | | | |
Allowance for loan losses | 0 | 0 | | | |
ASC 310-30 Loans | Construction, land and development | Acquired Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 31,188 | 13,167 | | | |
Allowance for loan losses | 143 | 145 | | 305 | |
ASC 310-30 Loans | Home equity loans and lines of credit | New Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 0 | 0 | | | |
Allowance for loan losses | 0 | 0 | | | |
ASC 310-30 Loans | Home equity loans and lines of credit | Acquired Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 202 | 0 | | | |
Allowance for loan losses | 0 | 0 | | 0 | |
ASC 310-30 Loans | Total other loans | New Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 0 | 0 | | | |
Allowance for loan losses | 0 | 0 | | | |
ASC 310-30 Loans | Total other loans | Acquired Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 23,807 | 14,054 | | | |
Allowance for loan losses | 248 | 271 | | | |
ASC 310-30 Loans | Commercial and industrial | New Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 0 | 0 | | | |
Allowance for loan losses | 0 | 0 | | | |
ASC 310-30 Loans | Commercial and industrial | Acquired Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 22,434 | 12,631 | | | |
Allowance for loan losses | 112 | 126 | | 1,310 | |
ASC 310-30 Loans | Consumer | New Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 0 | 0 | | | |
Allowance for loan losses | 0 | 0 | | | |
ASC 310-30 Loans | Consumer | Acquired Loans | | | | | |
Financing Receivable, Recorded Investment, Past Due [Line Items] | | | | | |
Loans - Recorded investment, ASC 310-30 loans | 1,373 | 1,423 | | | |
Allowance for loan losses | $ 136 | $ 145 | | $ 162 | |