Schedule II Financial Information of Registrant Parent Company Balance Sheet (Details) - USD ($) $ / shares in Units, $ in Thousands		Dec. 31, 2015	Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012
Assets
Fixed-maturities available for sale—at fair value (amortized cost $1,893,356 and $528,660)		$ 1,865,461	$ 536,890
Equity securities available for sale—at fair value (cost $75,538 and $76,900)		75,430	143,368
Trading securities—at fair value		1,279,137	1,633,584
Other short-term investments		1,076,944	1,300,872
Cash		46,898	30,465		$ 22,880	$ 29,408
Restricted cash		13,000	14,031
Investment in subsidiaries, at equity in net assets		2,900,000
Property and equipment, at cost (less accumulated depreciation of $51,567 and $50,648)	[1]	46,802	27,248
Other assets (Note H)		354,420	357,864
Assets held for sale		0	1,736,444	[2]
Total assets		5,642,100	6,842,336
LIABILITIES AND STOCKHOLDERS’ EQUITY
Long-term debt (Note 11)		1,219,454	1,192,299
Other liabilities		269,016	326,743
Liabilities held for sale		0	947,008
Total liabilities		3,145,169	4,670,586
Common stock: par value $.001 per share; 485,000,000 shares authorized at December 31, 2015 and 2014; 224,432,465 and 208,601,020 shares issued at December 31, 2015 and 2014, respectively; 206,871,768 and 191,053,530 shares outstanding at December 31, 2015 and 2014, respectively		224	209
Treasury stock, at cost: 17,560,697 and 17,547,490 shares at December 31, 2015 and 2014, respectively		(893,176)	(892,961)
Additional paid-in capital		2,716,618	2,531,513
Retained earnings		691,742	406,814
Accumulated other comprehensive (loss) income (“AOCI”) (Note 12)		(18,477)	51,485
Total common stockholders’ equity		2,496,931	2,097,060
Balance Sheet Parentheticals [Abstract]
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment		$ 106,900	$ 100,200
Common Stock, Par or Stated Value Per Share		$ 0.001	$ 0.001
Common Stock, Shares Authorized		485,000,000	485,000,000
Common Stock, Shares, Issued		224,432,465	208,601,020
Common Stock, Shares, Outstanding		206,871,768	191,053,530
Treasury Stock, Shares		17,560,697	17,547,490
Investments		$ 4,298,686	$ 3,629,299
Parent Company
Condensed Financial Statements, Captions [Line Items]
Notes Receivable, Related Parties		300,000	300,000
Assets
Fixed-maturities available for sale—at fair value (amortized cost $1,893,356 and $528,660)		41,176	0
Equity securities available for sale—at fair value (cost $75,538 and $76,900)		25,510	0
Trading securities—at fair value		5,482	5,447
Other short-term investments		158,658	631,934
Cash		3,301	1,951		$ 4,304	$ 2,978
Restricted cash		124	124
Investment in subsidiaries, at equity in net assets		3,001,846	2,746,915
Accounts and Notes Receivable, Net		631,636	305,856
Other assets (Note H)		124,983	31,394
Assets held for sale		0	18,027
Total assets		3,992,716	3,741,648
LIABILITIES AND STOCKHOLDERS’ EQUITY
Long-term debt (Note 11)		1,219,454	1,192,299
Federal income taxes—current and deferred		229,939	262,583
Other liabilities		46,392	96,989
Liabilities held for sale		0	18,027
Total liabilities		1,495,785	1,569,898
Equity component of currently redeemable convertible senior notes (Note 11)		0	74,690
Common stock: par value $.001 per share; 485,000,000 shares authorized at December 31, 2015 and 2014; 224,432,465 and 208,601,020 shares issued at December 31, 2015 and 2014, respectively; 206,871,768 and 191,053,530 shares outstanding at December 31, 2015 and 2014, respectively		224	209
Treasury stock, at cost: 17,560,697 and 17,547,490 shares at December 31, 2015 and 2014, respectively		(893,176)	(892,961)
Additional paid-in capital		2,716,618	2,531,513
Retained earnings		691,742	406,814
Accumulated other comprehensive (loss) income (“AOCI”) (Note 12)		(18,477)	51,485
Total common stockholders’ equity		2,496,931	2,097,060
Total liabilities and stockholders’ equity		3,992,716	3,741,648
Balance Sheet Parentheticals [Abstract]
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment		$ 0	$ 50,648
Common Stock, Par or Stated Value Per Share		$ 0.001	$ 0.001
Common Stock, Shares Authorized		485,000,000	485,000,000
Common Stock, Shares, Issued		0	208,601,020
Common Stock, Shares, Outstanding		0	191,053,530
Treasury Stock, Shares		0	17,547,490
Investments		$ 230,826	$ 637,381

[1] Property and equipment, at cost less accumulated depreciation of $106.9 million and $100.2 million at December 31, 2015 and 2014, respectively.

[2] Assets held for sale are not part of the Mortgage Insurance or Services segments.