Accumulated Other Comprehensive Income (Loss) - Summary of Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss at December 31, 2015			$ 673,447
Amounts reclassified from accumulated other comprehensive income			(25)
Other comprehensive income	$ 1,979	$ (509)	1,980	$ 1,464
Accumulated other comprehensive income at September 30, 2016	673,161		673,161
Unrealized Gains on Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss at December 31, 2015			(686)
Other comprehensive income before reclassifications			2,005
Accumulated other comprehensive income at September 30, 2016	1,294		1,294
Accumulated Other Comprehensive (Loss) Income
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss at December 31, 2015			(686)
Other comprehensive income			1,980
Accumulated other comprehensive income at September 30, 2016	$ 1,294		$ 1,294