Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 25,267	$ 22,574	$ 43,229	$ 42,456
Unrealized holding gains (losses):
Before tax	9,493	(11,690)	28,366	(5,378)
Tax effect	(3,795)	4,670	(11,341)	2,142
Net of tax	5,698	(7,020)	17,025	(3,236)
Reclassification of net gains included in net income:
Before tax	23	515	910	1,027
Tax effect	(9)	(211)	(364)	(420)
Net of tax	14	304	546	607
Net unrealized holding gains (losses)	5,684	(7,324)	16,479	(3,843)
Derivative Instruments
Before tax	924	(1,831)	5,199	(2,550)
Tax effect	(370)	728	(2,092)	1,016
Net of tax	554	(1,103)	3,107	(1,534)
Total other comprehensive income (loss)	6,238	(8,427)	19,586	(5,377)
Total comprehensive income	$ 31,505	$ 14,147	$ 62,815	$ 37,079