Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 54,287	$ 54,784	$ 101,856	$ 101,913
Available for sale securities:
Unrealized gains (losses) arising during the period	10,346	(24,303)	41,997	(11,563)
Income tax (expense) benefit related to unrealized gains	(4,004)	9,721	(16,253)	4,625
Reclassification adjustment for net realized gains in earnings	(162)	(19)	(858)	(135)
Income tax expense related to realized gains	63	9	332	54
Other comprehensive income (loss), net of tax	6,243	(14,592)	25,218	(7,019)
Comprehensive income	$ 60,530	$ 40,192	$ 127,074	$ 94,894

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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