Condensed Consolidating Financial Information (Statements of Cash Flows) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Condensed Financial Statements, Captions [Line Items]
Net cash provided by operating activities	$ 117,611	$ 78,825
Cash flows from investing activities:
Sale of investment securities	22,396	67,033
Maturities of investment securities	93,368	343
Purchase of investment securities	(109,891)	(56,691)
Proceeds from sale or liquidation of long-term investments	466	1,000
Purchase of long-term investments	(26,000)	(50)
Investments in real estate ventures	(8,454)	(11,806)
Distributions from investments in real estate ventures	23,338	17,983
Increase in cash surrender value of life insurance policies	(854)	(393)
(Increase) decrease in restricted assets	(1,235)	2,674
Payments to Acquire Notes Receivable	(1,500)	0
Investments in subsidiaries	0	0
Proceeds from sale of fixed assets	75	5
Capital expenditures	(8,346)	(7,615)
Pay downs of investment securities	1,620	4,926
Investments in real estate, net	(205)	(81)
Net cash (used in) provided by investing activities	(15,222)	17,328
Cash flows from financing activities:
Proceeds from issuance of debt	850,020	243,282
Deferred financing costs	(19,200)	(6,600)
Repayments of debt	(836,145)	(2,917)
Borrowings under revolver	110,979	89,695
Repayments on revolver	(129,479)	(80,223)
Capital contributions received	0	0
Intercompany dividends paid	0	0
Dividends and distributions on common stock	(104,750)	(97,846)
Contributions from non-controlling interest	0	248
Distributions to non-controlling interest	(165)	(7,422)
Proceeds from issuance of Vector common stock	43,230	0
Net cash (used in) provided by financing activities	(85,510)	138,217
Net increase in cash and cash equivalents	16,879	234,370
Cash and cash equivalents, beginning of period	393,530	240,368
Cash and cash equivalents, end of period	410,409	474,738
Consolidating Adjustments [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash provided by operating activities	(110,387)	(99,040)
Cash flows from investing activities:
Sale of investment securities	0	0
Maturities of investment securities	0	0
Purchase of investment securities	0	0
Proceeds from sale or liquidation of long-term investments	0	0
Purchase of long-term investments	0	0
Investments in real estate ventures	0	0
Distributions from investments in real estate ventures	0	0
Increase in cash surrender value of life insurance policies	0	0
(Increase) decrease in restricted assets	0	0
Payments to Acquire Notes Receivable	0
Investments in subsidiaries	5,749	987
Proceeds from sale of fixed assets	0	0
Capital expenditures	0	0
Pay downs of investment securities	0	0
Investments in real estate, net	0	0
Net cash (used in) provided by investing activities	5,749	987
Cash flows from financing activities:
Proceeds from issuance of debt	0	0
Deferred financing costs	0	0
Repayments of debt	0	0
Borrowings under revolver	0	0
Repayments on revolver	0	0
Capital contributions received	(5,749)	(987)
Intercompany dividends paid	110,387	99,040
Dividends and distributions on common stock	0	0
Contributions from non-controlling interest		0
Distributions to non-controlling interest	0	0
Proceeds from issuance of Vector common stock	0
Net cash (used in) provided by financing activities	104,638	98,053
Net increase in cash and cash equivalents	0	0
Cash and cash equivalents, beginning of period	0	0
Cash and cash equivalents, end of period	0	0
Parent/Issuer [Member]
Cash flows from investing activities:
Proceeds from sale or liquidation of long-term investments	0
Parent/Issuer [Member] | Reportable Legal Entities [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash provided by operating activities	58,546	73,915
Cash flows from investing activities:
Sale of investment securities	22,396	62,312
Maturities of investment securities	93,368	343
Purchase of investment securities	(109,891)	(56,691)
Proceeds from sale or liquidation of long-term investments		1,000
Purchase of long-term investments	(26,000)	0
Investments in real estate ventures	0	0
Distributions from investments in real estate ventures	0	0
Increase in cash surrender value of life insurance policies	(447)	0
(Increase) decrease in restricted assets	233	(7)
Payments to Acquire Notes Receivable	0
Investments in subsidiaries	(5,749)	(987)
Proceeds from sale of fixed assets	0	0
Capital expenditures	(6)	(26)
Pay downs of investment securities	1,620	4,926
Investments in real estate, net	0	0
Net cash (used in) provided by investing activities	(24,476)	10,870
Cash flows from financing activities:
Proceeds from issuance of debt	850,000	243,225
Deferred financing costs	(19,200)	(6,600)
Repayments of debt	(835,000)	0
Borrowings under revolver	0	0
Repayments on revolver	0	0
Capital contributions received	0	0
Intercompany dividends paid	0	0
Dividends and distributions on common stock	(104,750)	(97,846)
Contributions from non-controlling interest		0
Distributions to non-controlling interest	0	0
Proceeds from issuance of Vector common stock	43,230
Net cash (used in) provided by financing activities	(65,720)	138,779
Net increase in cash and cash equivalents	(31,650)	223,564
Cash and cash equivalents, beginning of period	279,815	111,470
Cash and cash equivalents, end of period	248,165	335,034
Subsidiary Guarantors [Member]
Cash flows from investing activities:
Proceeds from sale or liquidation of long-term investments	0
Subsidiary Guarantors [Member] | Reportable Legal Entities [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash provided by operating activities	138,336	75,513
Cash flows from investing activities:
Sale of investment securities	0	4,721
Maturities of investment securities	0	0
Purchase of investment securities	0	0
Proceeds from sale or liquidation of long-term investments		0
Purchase of long-term investments	0	0
Investments in real estate ventures	0	0
Distributions from investments in real estate ventures	0	0
Increase in cash surrender value of life insurance policies	(407)	(393)
(Increase) decrease in restricted assets	1,770	2,181
Payments to Acquire Notes Receivable	0
Investments in subsidiaries	0	0
Proceeds from sale of fixed assets	75	4
Capital expenditures	(2,049)	(3,716)
Pay downs of investment securities	0	0
Investments in real estate, net	0	0
Net cash (used in) provided by investing activities	(611)	2,797
Cash flows from financing activities:
Proceeds from issuance of debt	0	0
Deferred financing costs	0	0
Repayments of debt	(1,058)	(2,863)
Borrowings under revolver	110,979	89,695
Repayments on revolver	(129,479)	(80,223)
Capital contributions received	300	600
Intercompany dividends paid	(83,765)	(65,648)
Dividends and distributions on common stock	0	0
Contributions from non-controlling interest		0
Distributions to non-controlling interest	0	0
Proceeds from issuance of Vector common stock	0
Net cash (used in) provided by financing activities	(103,023)	(58,439)
Net increase in cash and cash equivalents	34,702	19,871
Cash and cash equivalents, beginning of period	14,798	12,375
Cash and cash equivalents, end of period	49,500	32,246
Subsidiary Non-Guarantors [Member]
Cash flows from investing activities:
Proceeds from sale or liquidation of long-term investments	466
Subsidiary Non-Guarantors [Member] | Reportable Legal Entities [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash provided by operating activities	31,116	28,437
Cash flows from investing activities:
Sale of investment securities	0	0
Maturities of investment securities	0	0
Purchase of investment securities	0	0
Proceeds from sale or liquidation of long-term investments		0
Purchase of long-term investments	0	(50)
Investments in real estate ventures	(8,454)	(11,806)
Distributions from investments in real estate ventures	23,338	17,983
Increase in cash surrender value of life insurance policies	0	0
(Increase) decrease in restricted assets	(3,238)	500
Payments to Acquire Notes Receivable	(1,500)
Investments in subsidiaries	0	0
Proceeds from sale of fixed assets	0	1
Capital expenditures	(6,291)	(3,873)
Pay downs of investment securities	0	0
Investments in real estate, net	(205)	(81)
Net cash (used in) provided by investing activities	4,116	2,674
Cash flows from financing activities:
Proceeds from issuance of debt	20	57
Deferred financing costs	0	0
Repayments of debt	(87)	(54)
Borrowings under revolver	0	0
Repayments on revolver	0	0
Capital contributions received	5,449	387
Intercompany dividends paid	(26,622)	(33,392)
Dividends and distributions on common stock	0	0
Contributions from non-controlling interest		248
Distributions to non-controlling interest	(165)	(7,422)
Proceeds from issuance of Vector common stock	0
Net cash (used in) provided by financing activities	(21,405)	(40,176)
Net increase in cash and cash equivalents	13,827	(9,065)
Cash and cash equivalents, beginning of period	98,917	116,523
Cash and cash equivalents, end of period	$ 112,744	$ 107,458