Income taxes: (Tables)

12 Months Ended

Dec. 31, 2017

Income taxes:

Schedule of components of income (loss) before income taxes

        The components of income (loss) before income taxes consist of the following (in thousands):

	Years Ended December 31,
	2017			2016			2015
Domestic	$	52,250		$	41,759		$	21,972
Foreign		(21,132	)		(17,499	)		(9,260	)
Total income before income taxes	$	31,118		$	24,260		$	12,712

Schedule of income tax expense

        The income tax expense is comprised of the following (in thousands):

	Years Ended December 31,
	2017			2016			2015
Current:
Federal	$	—		$	135		$	(9	)
State		(353	)		(188	)		4
Foreign		(209	)		(202	)		(96	)
Deferred:
Federal		(24,150	)		(8,175	)		(5,867	)
State		(430	)		(1,047	)		(1,959	)
Foreign		(100	)		146			111
Total income tax expense	$	(25,242	)	$	(9,331	)	$	(7,816	)

Schedule of net deferred tax assets

        Our consolidated temporary differences comprising our net deferred tax assets are as follows (in thousands):

	December 31,
	2017			2016
Deferred Tax Assets:
Net operating loss carry-forwards	$	271,219		$	273,509
Tax credits		2,771			2,237
Equity-based compensation		2,327			2,279
Total gross deferred tax assets		276,317			278,025
Deferred Tax Liabilities:
Depreciation and amortization		22,777			29,984
Accrued liabilities and other		106,251			95,606
Total gross deferred tax liabilities		129,028			125,590
Net deferred tax assets before valuation allowance		147,289			152,435
Valuation allowance		(129,673	)		(110,194	)
Net deferred tax assets	$	17,616		$	42,241

Schedule of reconciliation of unrecognized tax benefits

        A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (in thousands):

	Years Ended December 31,
	2017		2016			2015
Beginning balance of unrecognized tax benefits	$	—	$	776		$	866
Decrease attributable to settlements with taxing authorities		—		(776	)		—
Decrease attributable to lapses of statutes of limitation		—		—			(90	)
Ending balance of unrecognized tax benefits	$	—	$	—		$	776

Schedule of reconciliation of the Federal statutory income taxes to the amounts reported in the financial statements

        The following is a reconciliation of the Federal statutory income taxes to the amounts reported in the financial statements (in thousands).

	Years Ended December 31,
	2017			2016			2015
Federal income tax expense at statutory rates	$	(10,892	)	$	(8,492	)	$	(4,450	)
Effect of:
State income taxes, net of federal benefit		(2,244	)		(1,080	)		(1,710	)
Impact of foreign operations		74			138			(179	)
Non-deductible expenses		(1,350	)		(590	)		(1,253	)
Changes in tax reserves		—			175			128
Federal tax rate change		(9,046	)		—			—
Transition tax on foreign earnings		(2,296	)		—			—
Other		239			98			(16	)
Changes in valuation allowance		273			420			(336	)
Income tax expense	$	(25,242	)	$	(9,331	)	$	(7,816	)