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Fair Value Measurements - Schedule of Reconciliation of Debt Securities (Detail) - Debt Securities [Member] - Fair Value, Inputs, Level 3 [Member] - USD ($)
$ in Thousands
3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]    
Beginning balance $ 12,220 $ 12,658
Accrued interest income   316
Gains or losses recorded for the period    
Recognized in net income (5,585)  
Recognized in other comprehensive income 2,365 (824)
Ending balance $ 9,000 $ 12,150