Condensed Consolidating Financial Information (Statements of Cash Flows) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Condensed Financial Statements, Captions [Line Items]
Net cash provided by operating activities	$ 206,443	$ 121,443
Cash flows from investing activities:
Sale of investment securities	23,066	81,235
Maturities of investment securities	94,858	4,343
Purchase of investment securities	(120,362)	(90,106)
Proceeds from sale or liquidation of long-term investments	966	1,000
Purchase of long-term investments	(26,500)	(50)
Investments in real estate ventures	(20,830)	(23,358)
Acquisition of a business	(6,569)	0
Distributions from investments in real estate ventures	23,338	23,041
Increase in cash surrender value of life insurance policies	(831)	(451)
(Increase) decrease in restricted assets	(3,541)	8,615
Issuance of notes receivable	(1,633)	0
Repayments of notes receivable	0	4,410
Investments in subsidiaries	0	0
Proceeds from sale of fixed assets	75	45
Capital expenditures	(15,258)	(19,157)
Pay downs of investment securities	2,153	7,842
Investments in real estate, net	(357)	(130)
Net cash used in investing activities	(51,425)	(2,721)
Cash flows from financing activities:
Proceeds from issuance of debt	850,021	243,620
Deferred financing costs	(19,200)	(6,600)
Repayments of debt	(836,600)	(4,698)
Borrowings under revolver	121,521	104,826
Repayments on revolver	(152,870)	(94,644)
Capital contributions received	0	0
Intercompany dividends paid	0	0
Dividends and distributions on common stock	(158,425)	(147,270)
Contributions from non-controlling interest	0	248
Distributions to non-controlling interest	(165)	(9,508)
Proceeds from exercise of Vector options	0	398
Tax benefit of options exercised	0	412
Proceeds from issuance of Vector common stock	43,230	0
Net cash (used in) provided by financing activities	(152,488)	86,784
Net increase in cash and cash equivalents	2,530	205,506
Cash and cash equivalents, beginning of period	393,530	240,368
Cash and cash equivalents, end of period	396,060	445,874
Consolidating Adjustments [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash provided by operating activities	(159,728)	(156,635)
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
Acquisition of a business	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
Issuance of notes receivable	0
Repayments of notes receivable		0
Investments in subsidiaries	20,245	1,103
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 investing activities	20,245	1,103
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	(20,245)	(1,103)
Intercompany dividends paid	159,728	156,635
Dividends and distributions on common stock	0	0
Contributions from non-controlling interest		0
Distributions to non-controlling interest	0	0
Proceeds from exercise of Vector options		0
Tax benefit of options exercised		0
Proceeds from issuance of Vector common stock	0
Net cash (used in) provided by financing activities	139,483	155,532
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] | Reportable Legal Entities [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash provided by operating activities	91,858	87,016
Cash flows from investing activities:
Sale of investment securities	23,066	76,514
Maturities of investment securities	94,858	4,343
Purchase of investment securities	(120,362)	(90,106)
Proceeds from sale or liquidation of long-term investments	500	1,000
Purchase of long-term investments	(26,500)	0
Investments in real estate ventures	0	0
Acquisition of a business	0
Distributions from investments in real estate ventures	0	0
Increase in cash surrender value of life insurance policies	(371)	0
(Increase) decrease in restricted assets	231	(11)
Issuance of notes receivable	0
Repayments of notes receivable		0
Investments in subsidiaries	(20,245)	(1,103)
Proceeds from sale of fixed assets	0	0
Capital expenditures	(31)	(33)
Pay downs of investment securities	2,153	7,842
Investments in real estate, net	0	0
Net cash used in investing activities	(46,701)	(1,554)
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	(158,425)	(147,270)
Contributions from non-controlling interest		0
Distributions to non-controlling interest	0	0
Proceeds from exercise of Vector options		398
Tax benefit of options exercised		412
Proceeds from issuance of Vector common stock	43,230
Net cash (used in) provided by financing activities	(119,395)	90,165
Net increase in cash and cash equivalents	(74,238)	175,627
Cash and cash equivalents, beginning of period	279,815	111,470
Cash and cash equivalents, end of period	205,577	287,097
Subsidiary Guarantors [Member] | Reportable Legal Entities [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash provided by operating activities	231,182	136,255
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	0
Purchase of long-term investments	0	0
Investments in real estate ventures	0	0
Acquisition of a business	0
Distributions from investments in real estate ventures	0	0
Increase in cash surrender value of life insurance policies	(460)	(451)
(Increase) decrease in restricted assets	2,379	8,126
Issuance of notes receivable	0
Repayments of notes receivable		0
Investments in subsidiaries	0	0
Proceeds from sale of fixed assets	75	32
Capital expenditures	(2,682)	(5,619)
Pay downs of investment securities	0	0
Investments in real estate, net	0	0
Net cash used in investing activities	(688)	6,809
Cash flows from financing activities:
Proceeds from issuance of debt	0	0
Deferred financing costs	0	0
Repayments of debt	(1,465)	(4,602)
Borrowings under revolver	121,521	104,826
Repayments on revolver	(152,870)	(94,644)
Capital contributions received	550	700
Intercompany dividends paid	(124,783)	(116,785)
Dividends and distributions on common stock	0	0
Contributions from non-controlling interest		0
Distributions to non-controlling interest	0	0
Proceeds from exercise of Vector options		0
Tax benefit of options exercised		0
Proceeds from issuance of Vector common stock	0
Net cash (used in) provided by financing activities	(157,047)	(110,505)
Net increase in cash and cash equivalents	73,447	32,559
Cash and cash equivalents, beginning of period	14,798	12,375
Cash and cash equivalents, end of period	88,245	44,934
Subsidiary Non-Guarantors [Member] | Reportable Legal Entities [Member]
Condensed Financial Statements, Captions [Line Items]
Net cash provided by operating activities	43,131	54,807
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	466	0
Purchase of long-term investments	0	(50)
Investments in real estate ventures	(20,830)	(23,358)
Acquisition of a business	(6,569)
Distributions from investments in real estate ventures	23,338	23,041
Increase in cash surrender value of life insurance policies	0	0
(Increase) decrease in restricted assets	(6,151)	500
Issuance of notes receivable	(1,633)
Repayments of notes receivable		4,410
Investments in subsidiaries	0	0
Proceeds from sale of fixed assets	0	13
Capital expenditures	(12,545)	(13,505)
Pay downs of investment securities	0	0
Investments in real estate, net	(357)	(130)
Net cash used in investing activities	(24,281)	(9,079)
Cash flows from financing activities:
Proceeds from issuance of debt	21	395
Deferred financing costs	0	0
Repayments of debt	(135)	(96)
Borrowings under revolver	0	0
Repayments on revolver	0	0
Capital contributions received	19,695	403
Intercompany dividends paid	(34,945)	(39,850)
Dividends and distributions on common stock	0	0
Contributions from non-controlling interest		248
Distributions to non-controlling interest	(165)	(9,508)
Proceeds from exercise of Vector options		0
Tax benefit of options exercised		0
Proceeds from issuance of Vector common stock	0
Net cash (used in) provided by financing activities	(15,529)	(48,408)
Net increase in cash and cash equivalents	3,321	(2,680)
Cash and cash equivalents, beginning of period	98,917	116,523
Cash and cash equivalents, end of period	$ 102,238	$ 113,843