The component of interest expense representing the noncash expenses charged against earnings in the period to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate caption: Noncash Interest Expense.

No definition available.

Schedule II - Condensed Financial Information of Registrant (Condensed Statements of Cash Flows) (Details) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
	Aug. 01, 2016	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating activities
Net income		$ 120,796	$ (7,420)	$ 14,708	$ (44,841)	$ 33,776	$ 97,306	$ 82,845	$ 5,903	$ 83,243	$ 219,830	$ 126,023
Adjustments to reconcile net income to net cash provided by operating activities:
Change in fair value of 2015 notes embedded conversion derivative										543,465	(464,698)	32,321
Change in fair value of derivatives										(165,727)	334,300	(506,328)
Loss on extinguishment of debt										0	0	12,502
Share-based compensation										6,692	7,373	3,544
ESOP compensation										2,522	2,604	2,486
Deferred income taxes										(10,408)	41,916	(46,504)
Other										(14,089)	(15,962)	(8,948)
Changes in operating assets and liabilities:
Other assets										1,812	71	(2,771)
Other liabilities										(55,940)	75,794	(51,008)
Net cash provided by operating activities										1,414,322	504,804	707,786
Investing activities
Purchases of property, plant and equipment										(1,197)	(1,313)	(1,352)
Net cash used in investing activities										(4,499,045)	(5,577,205)	(2,947,749)
Financing activities
Financing fees incurred and deferred										(1,456)	0	(100)
Repayment of notes payable										0	(48,152)	(219,094)
Net proceeds from settlement of notes hedges and warrants										0	25,775	16,558
Proceeds from issuance of debt										100,000	0	0
Excess tax benefits realized from share-based compensation plans										527	3,649	5,184
Proceeds from issuance of common stock	$ 134,700									139,654	112,481	13,681
Dividends paid										(21,110)	(17,874)	(15,015)
Net cash provided by (used in) financing activities										3,478,240	4,768,636	2,043,948
Increase (decrease) in cash and cash equivalents										393,517	(303,765)	(196,015)
Cash and cash equivalents at beginning of year					397,749				701,514	397,749	701,514	897,529
Cash and cash equivalents at end of year		791,266				397,749				791,266	397,749	701,514
Cash paid during the year for interest:
Interest paid										39,647	39,118	42,989
Common Stock Issued in Extinguishment of Debt [Member]
Non-cash financing activity:
Common stock issued										0	0	95,993
Common Stock Issued to Settle Warrants That Have Expired [Member]
Non-cash financing activity:
Common stock issued										93	48	0
Parent Company [Member]
Operating activities
Net income										83,243	219,830	126,023
Adjustments to reconcile net income to net cash provided by operating activities:
Change in fair value of 2015 notes embedded conversion derivative										0	(4,516)	(15,227)
Provision for depreciation and amortization										1,946	1,613	2,081
Accrual of discount on equity security										(7)	(6)	(6)
Equity in undistributed income of subsidiaries										(65,635)	(209,698)	(134,890)
Accrual of discount on contingent convertible notes										0	698	4,417
Change in fair value of derivatives										(698)	6,377	15,619
Loss on extinguishment of debt										0	0	12,502
Accrual of discount on debenture issued to subsidiary trust										221	207	193
Share-based compensation										818	1,026	1,141
ESOP compensation										0	0	82
Deferred income taxes										2,117	8,967	6,439
Other										0	0	(2,235)
Changes in operating assets and liabilities:
Receivable from subsidiaries										(125)	93	2,208
Federal income tax recoverable										11,361	2,683	1,121
Other assets										(326)	(4)	378
Other liabilities										2,546	(1,664)	(7,256)
Net cash provided by operating activities										35,461	25,606	12,590
Investing activities
Capital contributions to subsidiaries										(255,000)	(120,000)	0
Purchases of property, plant and equipment										(54)	0	0
Net cash used in investing activities										(255,054)	(120,000)	0
Financing activities
Financing fees incurred and deferred										(1,456)	0	(100)
Repayment of notes payable										0	(48,152)	(219,094)
Net proceeds from settlement of notes hedges and warrants										0	25,775	16,558
Proceeds from issuance of debt										100,000	0	0
Excess tax benefits realized from share-based compensation plans										0	0	184
Proceeds from issuance of common stock										139,654	112,481	13,681
Dividends paid										(21,114)	(17,946)	(15,221)
Net cash provided by (used in) financing activities										217,084	72,158	(203,992)
Increase (decrease) in cash and cash equivalents										(2,509)	(22,236)	(191,402)
Cash and cash equivalents at beginning of year					$ 38,903				$ 61,139	38,903	61,139	252,541
Cash and cash equivalents at end of year		$ 36,394				$ 38,903				36,394	38,903	61,139
Parent Company [Member] \| Common Stock Issued in Extinguishment of Debt [Member]
Non-cash financing activity:
Common stock issued										0	0	95,993
Parent Company [Member] \| Common Stock Issued to Settle Warrants That Have Expired [Member]
Non-cash financing activity:
Common stock issued										93	48	0
Parent Company [Member] \| Notes and Loans Payable [Member]
Cash paid during the year for interest:
Interest paid										27,164	27,283	31,206
Parent Company [Member] \| Subordinated Debentures [Member]
Cash paid during the year for interest:
Interest paid										$ 12,454	$ 11,833	$ 11,765