Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 46,003	$ 47,569
Available for sale securities:
Unrealized gains arising during the period	4,142	31,651
Income tax expense related to unrealized gains	(1,604)	(12,249)
Reclassification adjustment for net realized losses (gains) in earnings	2	(696)
Income tax (benefit) expense related to realized gains	(1)	269
Other comprehensive income, net of tax	2,539	18,975
Comprehensive income	$ 48,542	$ 66,544

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

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

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Amount before tax and reclassification adjustments of unrealized holding gain (loss) on available-for-sale securities.

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