Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Other comprehensive income (loss):
Other comprehensive loss, before tax	$ (15,097)	$ (6,051)
Other comprehensive income (loss):
Other comprehensive loss, tax (expense) benefit	2,941	1,285
Net of Tax
Stockholders equity, beginning of period	1,119,241	955,738
Other comprehensive income (loss):
Other comprehensive loss, net of tax	(12,156)	(4,766)
Stockholders equity, end of period	1,343,773	1,119,241
Accumulated Other Comprehensive Income (Loss)
Before Tax
AOCI before tax, beginning of period	661	6,712
Other comprehensive income (loss):
AOCI before tax, end of period	(14,436)	661
Tax Effect
AOCI tax effect, beginning of period	(760)	(2,045)
Other comprehensive income (loss):
AOCI tax effect, end of period	2,181	(760)
Net of Tax
Stockholders equity, beginning of period	(99)	4,667
Other comprehensive income (loss):
Stockholders equity, end of period	(12,255)	(99)
Accumulated Net Investment Gain (Loss) Attributable to Parent
Other comprehensive income (loss):
Unrealized holding losses arising during the period, before tax	(13,156)	(3,216)
Less: Reclassification adjustment for gains included in net income	(1,941)	(2,835)
Other comprehensive loss, before tax	(15,097)	(6,051)
Other comprehensive income (loss):
Unrealized holding losses arising during the period, tax (expense) benefit	2,376	664
Less: Reclassification adjustment for gains included in net income	565	621
Other comprehensive loss, tax (expense) benefit	2,941	1,285
Other comprehensive income (loss):
Unrealized holding losses arising during the period, net of tax	(10,780)	(2,552)
Less: Reclassification adjustment for gains included in net income	(1,376)	(2,214)
Other comprehensive loss, net of tax	$ (12,156)	$ (4,766)