Revenue (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Total noninterest income in-scope of Topic 606									$ 71,612,000	$ 59,034,000	$ 50,304,000
Loan servicing income									7,292,000	5,636,000	4,501,000
Securities gains, net (includes $1,085, $6,764, and $11,518 of net security gains reclassified from accumulated other comprehensive income for the years ended December 31, 2018, 2017, and 2016, respectively)									1,085,000	6,973,000	11,340,000
Unrealized gain on equity securities, net									212,000	0	0
Net gains on sale of loans held for sale									21,450,000	22,251,000	39,634,000
Valuation allowance on servicing rights									(46,000)	21,000	(33,000)
Income on bank owned life insurance									2,793,000	2,772,000	2,275,000
Other noninterest income									4,762,000	5,335,000	5,580,000
Total noninterest income out-of-scope of Topic 606									37,548,000	42,988,000	63,297,000
TOTAL NONINTEREST INCOME	$ 27,045,000	$ 29,765,000	$ 27,634,000	$ 24,716,000	$ 25,528,000	$ 24,977,000	$ 25,624,000	$ 25,893,000	109,160,000	102,022,000	113,601,000
Service charges and fees on deposit accounts
Disaggregation of Revenue [Line Items]
Total noninterest income in-scope of Topic 606									11,291,000	9,570,000	8,314,000
Overdraft fees
Disaggregation of Revenue [Line Items]
Total noninterest income in-scope of Topic 606									10,796,000	9,365,000	8,300,000
Customer service fees
Disaggregation of Revenue [Line Items]
Total noninterest income in-scope of Topic 606									327,000	288,000	208,000
Credit card fee income
Disaggregation of Revenue [Line Items]
Total noninterest income in-scope of Topic 606									11,893,000	7,968,000	4,866,000
Debit card income
Disaggregation of Revenue [Line Items]
Total noninterest income in-scope of Topic 606									14,396,000	11,984,000	9,873,000
Other service charges
Disaggregation of Revenue [Line Items]
Total noninterest income in-scope of Topic 606									3,000	8,000	29,000
Total service charges and fees
Disaggregation of Revenue [Line Items]
Total noninterest income in-scope of Topic 606									48,706,000	39,183,000	31,590,000
Trust fees
Disaggregation of Revenue [Line Items]
Total noninterest income in-scope of Topic 606									18,393,000	15,818,000	14,845,000
Brokerage and insurance commissions
Disaggregation of Revenue [Line Items]
Total noninterest income in-scope of Topic 606									$ 4,513,000	$ 4,033,000	$ 3,869,000