Premises and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Premises and equipment
Total	$ 278,761	$ 267,293
Less accumulated depreciation	(104,224)	(95,521)
Net premises and equipment	174,537	171,772
Depreciation expense charged to operations	11,100	11,100	$ 10,000
Amortization expense	1,800	1,700	$ 1,400
Land
Premises and equipment
Total	55,590	54,269
Buildings and leasehold improvements
Premises and equipment
Total	$ 139,946	139,742
Buildings and leasehold improvements | Minimum
Premises and equipment
Useful Life	15 years
Buildings and leasehold improvements | Maximum
Premises and equipment
Useful Life	40 years
Equipment and furnishings
Premises and equipment
Total	$ 79,585	72,671
Equipment and furnishings | Minimum
Premises and equipment
Useful Life	3 years
Equipment and furnishings | Maximum
Premises and equipment
Useful Life	10 years
Construction in process
Premises and equipment
Total	$ 3,640	611
Computer software
Premises and equipment
Useful Life	36 months
Total	$ 6,300	$ 6,000