CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands		Total	Common Stock [Member]	Preferred Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]
Beginning Balance at Dec. 31, 2013		$ 175,609	$ 436		$ 42,282	$ 168,734	$ (376)	$ (35,467)
Beginning balance, shares at Dec. 31, 2013			43,641	30
Stock option exercises		(6,036)	$ 19		9,347			(15,402)
Stock option exercises, shares			1,900
Grants and vesting of restricted stock		(11,545)	$ 10		(10)			(11,545)
Grants and vesting of restricted stock, shares			950
Conversion of preferred stock			$ 1		(1)
Conversion of preferred stock, shares			65	(18)
Purchases of treasury stock		(29,736)						$ (29,736)
Purchases of treasury stock, shares								2,392
Treasury shares reissued					(3,050)			$ 3,050
Retirement of treasury shares			$ (18)		(26,929)			$ 26,947
Retirement of treasury shares, shares			(1,787)					1,787
Share-based compensation		12,342			12,342
Net income		72,988				72,988
Change in net unrealized gains (losses)	[1]	(1,459)					(1,459)
Excess tax benefit (shortfall), net	[2]	7,006			7,006
Declaration of dividends		(19,253)				(19,253)
Ending Balance at Dec. 31, 2014		199,916	$ 448		40,987	222,469	(1,835)	$ (62,153)
Ending balance, shares at Dec. 31, 2014			44,769	12
Stock option exercises		(4,287)	$ 7		3,807			(8,101)
Stock option exercises, shares			751
Grants and vesting of restricted stock		(7,344)	$ 6		(6)			(7,344)
Grants and vesting of restricted stock, shares			615
Purchase of preferred stock		(256)			(256)
Purchase of preferred stock, shares				(2)
Purchases of treasury stock		(18,649)						$ (18,649)
Purchases of treasury stock, shares								748
Reclassification of contingently redeemable common stock to common stock		19,000			19,000
Retirement of treasury shares			$ (6)		(15,439)			$ 15,445
Retirement of treasury shares, shares			(610)					610
Share-based compensation		17,386			17,386
Net income		106,484				106,484
Change in net unrealized gains (losses)	[1]	(2,171)					(2,171)
Excess tax benefit (shortfall), net	[2]	5,310			5,310
Declaration of dividends		(22,297)				(22,297)
Ending Balance at Dec. 31, 2015		293,092	$ 455		70,789	306,656	(4,006)	$ (80,802)
Ending balance, shares at Dec. 31, 2015			45,525	10
Stock option exercises		$ (5,332)	$ 1		905			(6,238)
Stock option exercises, shares		124	124
Purchases of treasury stock		$ (8,510)						$ (8,510)
Purchases of treasury stock, shares								441
Treasury shares reissued		10,000			7,670			$ 2,330
Retirement of treasury shares			$ (3)		(6,235)			$ 6,238
Retirement of treasury shares, shares			(325)					325
Share-based compensation		10,288			10,288
Net income		99,410				99,410
Change in net unrealized gains (losses)	[1]	(2,402)					(2,402)
Excess tax benefit (shortfall), net	[2]	(1,154)			(1,154)
Declaration of dividends		(24,202)				(24,202)
Ending Balance at Dec. 31, 2016		$ 371,190	$ 453		$ 82,263	$ 381,864	$ (6,408)	$ (86,982)
Ending balance, shares at Dec. 31, 2016			45,324	10

[1] Represents change in fair value of available for sale investments, net of tax benefit of $1,486 thousand, $1,369 thousand and $916 thousand in years ended December 31, 2016, 2015 and 2014, respectively.

[2] Excess tax benefit (shortfall) relate to share-based compensation.