Unaudited Condensed Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 27,670us-gaap_NetIncomeLoss	$ 26,730us-gaap_NetIncomeLoss
Other Comprehensive Income, Net of Tax
Unrealized gains on available-for-sale securities	5,181	14,603
Reclassification adjustment for (gains) losses included in net income	(4)	73
Net unrealized gains on available-for-sale securities	5,177	14,676
Tax effect	(1,979)	(5,680)
Net of tax amount	3,198	8,996
Unrealized losses on derivatives used for cash flow hedges	(5,993)	(5,479)
Reclassification adjustment for losses included in net income	1,251	0
Net unrealized losses on derivatives used for cash flow hedges	(4,742)	(5,479)
Tax effect	1,827	2,126
Net of tax amount	(2,915)	(3,353)
Total other comprehensive income, net of tax	283	5,643
Total Comprehensive Income	$ 27,953us-gaap_ComprehensiveIncomeNetOfTax	$ 32,373us-gaap_ComprehensiveIncomeNetOfTax

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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Amount before tax, after reclassification adjustments, of appreciation (loss) in value of unsold available-for-sale securities. Excludes amounts related to other than temporary impairment (OTTI) loss.

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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Amount before tax of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities.

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