Operating Expenses (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating Expenses [Abstract]
Salaries and wages									$ 135,407	$ 104,490	$ 83,229
Employee benefits									29,806	23,430	19,328
Occupancy									23,525	18,213	15,842
Equipment and software									24,408	18,569	14,737
Outside processing and service fees									21,199	15,207	11,586
FDIC insurance premiums									7,407	5,485	4,307
Professional fees									5,832	4,842	3,570
Intangible asset amortization									5,524	4,389	2,029
Postage and express mail									3,777	3,313	3,418
Advertising and marketing									3,740	3,288	3,051
Training, travel and other employee expenses									4,025	3,224	2,480
Telephone									2,964	2,608	1,966
Supplies									2,318	2,216	1,897
Donations									1,951	1,375	1,155
Credit-related expenses									(2,701)	632	996
Merger and acquisition-related transaction expenses									61,134	7,804	6,388
Other									8,102	4,809	3,946
Total operating expenses	$ 114,302	$ 106,144	$ 59,085	$ 58,887	$ 57,824	$ 58,265	$ 56,785	$ 51,020	$ 338,418	$ 223,894	$ 179,925