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VALUATION AND QUALIFYING ACCOUNTS
12 Months Ended
Dec. 31, 2017
Valuation and Qualifying Accounts [Abstract]  
VALUATION AND QUALIFYING ACCOUNTS
SCHEDULE II
SPOK HOLDINGS, INC.
VALUATION AND QUALIFYING ACCOUNTS
 
Allowance for Doubtful Accounts,
Service Credits and Other
 
Balance at the
Beginning of
the Period
 
Charged to
Operations
 
Write-offs
 
Balance at the
End of the
Period
 
 
(Dollars in thousands)
Year ended December 31, 2017
 
$
1,056

 
$
1,035

 
$
(1,026
)
 
$
1,065

Year ended December 31, 2016
 
$
1,286

 
$
761

 
$
(991
)
 
$
1,056

Year ended December 31, 2015
 
$
1,300

 
$
1,290

 
$
(1,304
)
 
$
1,286

 
 
 
 
 
 
 
 
 
Deferred Income Tax Asset Valuation
Allowance
 
Balance at the
Beginning of
the Period
 
Additions
 
Deductions
 
Balance at the
End of the
Period
 
 
(Dollars in thousands)
Year ended December 31, 2017
 
$

 
$

 
$

 
$

Year ended December 31, 2016
 
$
50,031

 
$

 
$
(50,031
)
 
$

Year ended December 31, 2015
 
$
114,190

 
$

 
$
(64,159
)
 
$
50,031