Basis of Presentation and Significant Accounting Policies - Condensed Balance Sheet, Pro Forma Amounts Under Previous Guidance (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Assets
Contract assets	$ 22,269	$ 29,759	$ 0
Inventories, net	139,408	138,759	162,589
Prepaid expenses and other current assets	12,229	11,513	11,687
Deferred income taxes	7,119	7,811	7,913
Liabilities and Stockholders' Equity
Accounts payable and other current liabilities	319,350
Deferred income taxes	4,485	4,443	4,423
Retained earnings	270,277	270,864	$ 266,780
Without Adoption of ASU 2014-09
Assets
Contract assets	0
Inventories, net	156,478
Prepaid expenses and other current assets	12,313
Deferred income taxes	7,141
Liabilities and Stockholders' Equity
Accounts payable and other current liabilities	317,921
Deferred income taxes	4,359
Retained earnings	266,739
Effect of Change | ASU 2014-09
Assets
Contract assets	22,269	29,759
Inventories, net	(17,070)	(23,830)
Prepaid expenses and other current assets	(84)	(174)
Deferred income taxes	(22)	(102)
Liabilities and Stockholders' Equity
Accounts payable and other current liabilities	1,429
Deferred income taxes	126	20
Retained earnings	$ 3,538	$ 4,084