Segment Reporting (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) segment	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Segment Reporting [Abstract]
Number of operating segments (segment) | segment			2
Segment Reporting Information [Line Items]
Net interest income	$ 73,681	$ 59,724	$ 219,506	$ 171,298
Provision for loan losses	5,328	3,181	9,513	10,526
Total noninterest income	28,542	24,980	89,146	86,304
Total noninterest expense	68,427	61,996	209,756	185,092
Income before taxes	28,468	19,527	89,383	61,984
Average Loans, for the period	5,538,088	4,654,179	5,493,187	4,457,715
Segment Assets, at period end	8,202,215	6,805,884	8,202,215	6,805,884	$ 7,694,754
Community and Other Banking
Segment Reporting Information [Line Items]
Net interest income	72,694	58,123	216,172	167,000
Provision for loan losses	5,328	3,181	9,513	10,526
Total noninterest income	17,337	16,015	55,773	48,679
Total noninterest expense	57,988	49,168	177,421	145,614
Income before taxes	26,715	21,789	85,011	59,539
Average Loans, for the period	5,464,304	4,563,221	5,422,843	4,365,908
Segment Assets, at period end	8,084,810	6,676,526	8,084,810	6,676,526
Retail Mortgage Banking
Segment Reporting Information [Line Items]
Net interest income	987	1,601	3,334	4,298
Provision for loan losses	0	0	0	0
Total noninterest income	11,205	8,965	33,373	37,625
Total noninterest expense	10,439	12,828	32,335	39,478
Income before taxes	1,753	(2,262)	4,372	2,445
Average Loans, for the period	73,784	90,958	70,344	91,807
Segment Assets, at period end	$ 117,405	$ 129,358	$ 117,405	$ 129,358