CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net income	$ 147,951us-gaap_NetIncomeLoss	$ 114,965us-gaap_NetIncomeLoss	$ 72,639us-gaap_NetIncomeLoss
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, Net of Tax	8,976	0	0
Other comprehensive income (loss), net:
Unrealized gain on transfer of HTM securities to AFS, net of tax effect of $(5,367) for the respective period presented	29,683	(30,503)	15,842
Unrealized loss on cash flow hedge, net of tax effect of $0, $10, $284 for each respective period presented	0	(17)	(502)
Realized (gain) loss on sale of AFS securities included in income, net of tax effect of $283, $(447), $1,428, for each respective period presented	(474)	748	(2,521)
Net other comprehensive income (loss)	38,185	(29,772)	12,819
Comprehensive income	$ 186,136us-gaap_ComprehensiveIncomeNetOfTax	$ 85,193us-gaap_ComprehensiveIncomeNetOfTax	$ 85,458us-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 after 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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Amount after tax, before reclassification adjustments, of unrealized holding gain (loss) related to transfers of securities into the available-for-sale classification and out of the held-to-maturity classification.

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Amount of unrealized gain (loss) related to derivatives designated as cash flow hedging instruments, recorded in results of operations to the extent that the cash flow hedge is determined to be ineffective.

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