UNAUDITED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - 6 months ended Jun. 30, 2018 - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Earnings
Balance at beginning of period at Dec. 31, 2017	$ 1,188,202	$ 565	$ 686,962	$ (172,407)	$ 673,082
Balance beginning of period (in shares) at Dec. 31, 2017		56,501
Increase (Decrease) in Stockholders' Equity
Net income	18,116				18,116
Other comprehensive loss	(21,688)			(21,688)
Stock-based compensation	6,639		6,639
Issuance of restricted shares, net of shares remitted and tax withholdings	(2,175)	$ 1	(2,176)
Issuance of restricted shares, net of shares remitted and tax withholdings (in shares)		118
Repurchases of common stock	$ (26,482)	$ (5)	(26,477)
Repurchases of common stock (in shares)	(500)	(532)
Balance at end of period at Jun. 30, 2018	$ 1,161,048	$ 561	$ 664,948	$ (194,095)	689,634
Balance ending of period (in shares) at Jun. 30, 2018		56,087
Increase (Decrease) in Stockholders' Equity
Cumulative effect of change in accounting principle	$ (1,564)
Cumulative effect of change in accounting principle | Accounting Standards Update 2016-16					$ (1,564)