Segment Reporting (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) segment	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Segment Reporting [Abstract]
Number of operating segments (segment) | segment			2
Segment Reporting Information [Line Items]
Net interest income	$ 89,844	$ 73,681	$ 237,452	$ 219,506
Provision for loan losses	5,705	5,328	10,235	9,513
Total noninterest income	24,977	28,542	76,494	89,146
Total noninterest expense	78,759	68,427	219,797	209,756
INCOME BEFORE INCOME TAXES	30,357	28,468	83,914	89,383
Average Loans, for the period	6,286,284	5,538,088	5,679,620	5,493,187
Segment Assets, at period end	9,755,627	8,202,215	9,755,627	8,202,215	$ 8,247,079
Community and Other Banking
Segment Reporting Information [Line Items]
Net interest income	88,778	72,694	234,406	216,172
Provision for loan losses	5,705	5,328	10,235	9,513
Total noninterest income	19,680	17,337	56,964	55,773
Total noninterest expense	69,977	57,988	193,753	177,421
INCOME BEFORE INCOME TAXES	32,776	26,715	87,382	85,011
Average Loans, for the period	6,245,445	5,464,304	5,641,641	5,422,843
Segment Assets, at period end	9,693,172	8,084,810	9,693,172	8,084,810
Retail Mortgage Banking
Segment Reporting Information [Line Items]
Net interest income	1,066	987	3,046	3,334
Provision for loan losses	0	0	0	0
Total noninterest income	5,297	11,205	19,530	33,373
Total noninterest expense	8,782	10,439	26,044	32,335
INCOME BEFORE INCOME TAXES	(2,419)	1,753	(3,468)	4,372
Average Loans, for the period	40,839	73,784	37,979	70,344
Segment Assets, at period end	$ 62,455	$ 117,405	$ 62,455	$ 117,405