Stockholders' Equity - Reconciliation of Beginning and End of Period Equity Accounts (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ 1,248,221	$ 1,232,443	$ 1,204,025	$ 1,185,756	$ 1,232,443	$ 1,185,756
Net income	9,258	7,180	15,709	8,983	16,438	24,692
Other comprehensive income	297	14,150	(24,479)	30,520	14,447	6,041
Share repurchase program			0	(15,565)
Stock compensation plans	1,517	(290)	1,092	(335)
Cash dividends	(5,267)	(5,262)	(5,289)	(5,334)
Ending Balance	$ 1,254,026	$ 1,248,221	$ 1,177,268	$ 1,204,025	1,254,026	1,177,268
Dividends paid (in dollars per share)	$ 105.000	$ 0.105	$ 105.000	$ 0.105
Total Parent Stockholders’ Equity
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ 1,186,641	$ 1,172,043	$ 1,140,721	$ 1,127,096	1,172,043	1,127,096
Net income	8,821	6,980	15,008	8,284
Other comprehensive income	637	13,170	(19,395)	26,575
Share repurchase program			(13,790)	(15,565)
Stock compensation plans	1,517	(290)	1,092	(335)
Cash dividends	(5,267)	(5,262)	(5,289)	(5,334)
Ending Balance	1,192,349	1,186,641	1,118,347	1,140,721	1,192,349	1,118,347
Noncontrolling Shareholders’ Interests in Consolidated Subsidiaries
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	61,580	60,400	63,304	58,660	60,400	58,660
Net income	437	200	701	699
Other comprehensive income	(340)	980	(5,084)	3,945
Ending Balance	$ 61,677	$ 61,580	$ 58,921	$ 63,304	$ 61,677	$ 58,921