Recently Adopted and Recently Issued Accounting Standards - Consolidated Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income	$ 145,013	$ 11,844	$ (79,753)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Deferred income tax expense (benefit)	(6,522)	57,349	(7,654)
Changes in assets and liabilities:
Accounts receivable	(16,881)	(32,012)	16,041
Inventories	(14,706)	19,557	(12,313)
Contract assets	(3,312)	0	0
Advances on contracts	3,057	(16,811)	14,485
Other assets and liabilities	(33,527)	3,368	(13,314)
Net cash used by operating activities	192,022	$ 176,892	$ 159,876
Impact of Adoption | Accounting Standards Update 2014-09
Cash flows from operating activities:
Net income	(2,679)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Deferred income tax expense (benefit)	(1,446)
Changes in assets and liabilities:
Accounts receivable	(13,143)
Inventories	10,330
Contract assets	3,312
Advances on contracts	(1,378)
Other assets and liabilities	5,004
Net cash used by operating activities	0
As Reported
Cash flows from operating activities:
Net income	142,334
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Deferred income tax expense (benefit)	(7,968)
Changes in assets and liabilities:
Accounts receivable	(30,024)
Inventories	(4,376)
Contract assets	0
Advances on contracts	1,679
Other assets and liabilities	(28,523)
Net cash used by operating activities	$ 192,022