Stockholders’ Equity (Deficit) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Increase (Decrease) in Stockholders' Equity
Balances, beginning of period	$ 188,561	$ (103,660)
Cumulative effect of accounting changes			$ (12,207)
Net income	53,513	65,133
Other comprehensive income (loss)	20,178	26,302
Dividends paid	(35,016)	(34,567)
Issuance of common stock	(3,409)	(5,184)
Conversion to common stock	0	0
Stock-based compensation expense	3,273	5,638
Balances, end of period	214,893	(46,338)
Preferred stock
Increase (Decrease) in Stockholders' Equity
Balances, beginning of period	1	1
Balances, end of period	1	1
Preference stock
Increase (Decrease) in Stockholders' Equity
Balances, beginning of period	441	483
Conversion to common stock	(19)	(5)
Balances, end of period	422	478
Common stock
Increase (Decrease) in Stockholders' Equity
Balances, beginning of period	323,338	323,338
Balances, end of period	323,338	323,338
Additional paid-in capital
Increase (Decrease) in Stockholders' Equity
Balances, beginning of period	138,367	148,125
Issuance of common stock	(21,607)	(27,098)
Conversion to common stock	(386)	(101)
Stock-based compensation expense	3,273	5,638
Balances, end of period	119,647	126,564
Retained earnings
Increase (Decrease) in Stockholders' Equity
Balances, beginning of period	5,229,584	5,107,734
Cumulative effect of accounting changes			$ (12,207)
Net income	53,513	65,133
Dividends paid	(35,016)	(34,567)
Balances, end of period	5,235,874	5,138,300
Accumulated other comprehensive loss
Increase (Decrease) in Stockholders' Equity
Balances, beginning of period	(792,173)	(940,133)
Other comprehensive income (loss)	20,178	26,302
Balances, end of period	(771,995)	(913,831)
Treasury stock
Increase (Decrease) in Stockholders' Equity
Balances, beginning of period	(4,710,997)	(4,743,208)
Issuance of common stock	18,198	21,914
Conversion to common stock	405	106
Balances, end of period	$ (4,692,394)	$ (4,721,188)