Accumulated Other Comprehensive Loss - Summary of Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss beginning balance	$ (1,325)	$ (7,517)
Other comprehensive income before reclassifications	3,428	(2,689)
Amounts reclassified from accumulated other comprehensive loss	(2,789)	8,881
Total other comprehensive income, net of tax	639	6,192	$ 1,135
Accumulated other comprehensive loss ending balance	(686)	(1,325)	(7,517)
Defined Benefit Pension Items
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss beginning balance	0	(5,392)
Other comprehensive income before reclassifications	0	(2,180)
Amounts reclassified from accumulated other comprehensive loss	0	7,572
Total other comprehensive income, net of tax	0	5,392
Accumulated other comprehensive loss ending balance	0	0	(5,392)
Unrealized Gains and (Losses) on Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss beginning balance	(1,325)	(2,125)
Other comprehensive income before reclassifications	3,428	(509)
Amounts reclassified from accumulated other comprehensive loss	(2,789)	1,309
Total other comprehensive income, net of tax	639	800
Accumulated other comprehensive loss ending balance	$ (686)	$ (1,325)	$ (2,125)