Stockholders' Equity - Reconciliation of Beginning and End of Period Equity Accounts (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ 1,254,026	$ 1,248,221	$ 1,232,443	$ 1,177,269	$ 1,204,025	$ 1,185,756	$ 1,232,443	$ 1,185,756
Net income	29,008	9,258	7,180	55,433	15,709	8,983	45,447	80,125
Other comprehensive income	(9,979)	297	14,150	860	(24,478)	30,520	4,468	6,902
Share repurchase program				(828)	0	(15,565)
Stock compensation plans	678	1,517	(290)	1,032	1,092	(335)
Cash dividends	(5,270)	(5,267)	(5,262)	(5,257)	(5,289)	(5,334)
Ending Balance	$ 1,268,463	$ 1,254,026	$ 1,248,221	$ 1,228,509	$ 1,177,269	$ 1,204,025	1,268,463	1,228,509
Dividends paid (in dollars per share)	$ 0.105	$ 0.105	$ 0.105	$ 0.105	$ 0.105	$ 0.105
Total Parent Stockholders’ Equity
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ 1,192,349	$ 1,186,641	$ 1,172,043	$ 1,118,347	$ 1,140,721	$ 1,127,096	1,172,043	1,127,096
Net income	29,344	8,821	6,980	53,713	15,008	8,284
Other comprehensive income	(7,991)	637	13,170	537	(19,395)	26,575
Share repurchase program				(828)	(13,790)	(15,565)
Stock compensation plans	678	1,517	(290)	1,032	1,092	(335)
Cash dividends	(5,270)	(5,267)	(5,262)	(5,257)	(5,289)	(5,334)
Ending Balance	1,209,110	1,192,349	1,186,641	1,167,544	1,118,347	1,140,721	1,209,110	1,167,544
Noncontrolling Shareholders’ Interests in Consolidated Subsidiaries
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	61,677	61,580	60,400	58,922	63,304	58,660	60,400	58,660
Net income	(336)	437	200	1,720	701	699
Other comprehensive income	(1,988)	(340)	980	323	(5,083)	3,945
Ending Balance	$ 59,353	$ 61,677	$ 61,580	$ 60,965	$ 58,922	$ 63,304	$ 59,353	$ 60,965