Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement of Comprehensive Income [Abstract]
Net Income	$ 116,127	$ 112,755	$ 95,644
Other Comprehensive (Loss) Income, Net of Tax
Unrealized (losses) gains on available-for-sale securities	(22,845)	31,569	(81,739)
Reclassification adjustment for (gains) losses included in net income	(69)	204	299
Net unrealized (losses) gains on available-for-sale securities	(22,914)	31,773	(81,440)
Tax effect	8,904	(12,313)	31,680
Net of tax amount	(14,010)	19,460	(49,760)
Unrealized (losses) gains on derivatives used for cash flow hedges	(7,857)	(19,557)	18,728
Reclassification adjustment for losses included in net income	5,025	993	0
Net unrealized (losses) gains on derivatives used for cash flow hedges	(2,832)	(18,564)	18,728
Tax effect	1,087	7,203	(7,285)
Net of tax amount	(1,745)	(11,361)	11,443
Total other comprehensive (loss) income, net of tax	(15,755)	8,099	(38,317)
Total Comprehensive Income	$ 100,372	$ 120,854	$ 57,327