Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common stock	Additional paid-in capital	Retained earnings	Accumulated Other Comprehensive Income (Loss)	Unrealized investment gain	Currency Translation Adjustments	Treasury stock	Noncontrolling interest
Beginning of period at Dec. 31, 2016		$ 47,024	$ 1,037,446	$ 6,595,987		$ 427,154	$ (371,586)	$ (2,688,817)	$ 33,926
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock units issued			(667)
Restricted stock units expensed			10,810
Cumulative effect adjustment resulting from changes in accounting principles				0		0
Net income before noncontrolling interests	$ 124,674			123,447					1,227
Dividends				(15,759)
Unrealized losses on securities not other-than-temporarily impaired	(8,831)					(8,913)
Unrealized gains on other-than-temporarily impaired securities						101
Net change in period	22,735						22,735
Stock exercised/vested								644
Stock repurchased								0
(Distributions) contributions									3,801
Other comprehensive income (loss), net of tax	13,904				$ 13,904		22,735		(19)
End of period at Mar. 31, 2017			1,047,589	6,703,675	69,491	418,342	(348,851)	(2,688,173)	38,935
Beginning of period at Dec. 31, 2017	5,451,163	$ 47,024	1,048,283	6,956,882		375,421	(306,880)	(2,709,386)	39,819
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Restricted stock units issued			(487)
Restricted stock units expensed			9,434
Cumulative effect adjustment resulting from changes in accounting principles				215,939		(214,539)
Net income before noncontrolling interests	167,573			166,396					1,177
Dividends				(17,016)
Unrealized losses on securities not other-than-temporarily impaired	(125,772)					(125,796)
Unrealized gains on other-than-temporarily impaired securities						13
Net change in period	12,799						12,799
Stock exercised/vested								488
Stock repurchased								(6,799)
(Distributions) contributions									(603)
Other comprehensive income (loss), net of tax	(112,973)				(112,973)		12,799		11
End of period at Mar. 31, 2018	$ 5,492,180		$ 1,057,230	$ 7,322,201	$ (258,982)	$ 35,099	$ (294,081)	$ (2,715,697)	$ 40,404