Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 17,962	$ 19,882
Unrealized holding gains:
Before tax	18,873	6,312
Tax effect	(7,546)	(2,528)
Net of tax	11,327	3,784
Reclassification of net gains included in net income:
Before tax	887	512
Tax effect	(355)	(209)
Net of tax	532	303
Net unrealized holding gains	10,795	3,481
Unrealized holding gains (losses):
Before tax	4,275	(719)
Tax effect	(1,722)	288
Net of tax	2,553	(431)
Total other comprehensive income	13,348	3,050
Total comprehensive income	$ 31,310	$ 22,932