Basis of Presentation and Significant Accounting Policies - Adjustments Made to the Consolidated Balance Sheet Following Adoption (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 tax assets	7,119	7,811	7,913
Liabilities and Stockholders' Equity
Accounts payable and other current liabilities		334,463
Deferred income tax liabilities	4,485	4,443	4,423
Retained earnings	270,277	270,864	266,780
As reported
Assets
Contract assets	0
Inventories, net	156,478
Prepaid expenses and other current assets	12,313
Deferred income tax assets	7,141
Liabilities and Stockholders' Equity
Accounts payable and other current liabilities			$ 332,935
Deferred income tax liabilities	4,359
Retained earnings	266,739
ASU 2014-09 | Adjustments due to Adoption of 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 tax assets	(22)	(102)
Liabilities and Stockholders' Equity
Accounts payable and other current liabilities		1,528
Deferred income tax liabilities	126	20
Retained earnings	$ 3,538	$ 4,084