Stockholders' Equity - Reconciliation of Beginning and End of Period Equity Accounts (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance			$ 1,130,236
Net income (loss)	$ 45,824	$ 71,351	75,206	$ 130,123
Other comprehensive income	15,526	$ (10,269)	36,534	$ (7,637)
Share repurchase program			(38,567)
Stock compensation plans			594
Cash dividends - $0.210 per share			(11,081)
Ending Balance	$ 1,192,922		$ 1,192,922
Cash dividends per share (in dollars per share)	$ 0.105	$ 0.105	$ 0.210	$ 0.21
Total Parent Stockholders’ Equity
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance			$ 1,076,014
Net income (loss)			75,872
Other comprehensive income			32,355
Share repurchase program			(38,567)
Stock compensation plans			594
Cash dividends - $0.210 per share			(11,081)
Ending Balance	$ 1,135,187		1,135,187
Noncontrolling Shareholders’ Interests in Consolidated Subsidiary
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance			54,222
Net income (loss)			(666)
Other comprehensive income			4,179
Ending Balance	$ 57,735		$ 57,735