Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash flows from operating activities:
Net income	$ 340,074	$ 174,560	$ 304,442
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	32,245	31,259	27,145
Current and deferred tax expense	185,106	104,343	136,229
Share-based compensation expense	190,054	320,786	30,115
Impairment write downs			6,804
Amortization of debt discount and debt issue costs	12,456	12,601	11,064
Amortization of discount or premium on investments	5,231	4,501	4,604
Other	6,493	3,182	14,471
Excess tax benefits from share-based compensation	(30,845)	(9,299)	(3,054)
Changes in assets and liabilities:
Accounts receivable	(35,689)	(10,027)	(23,991)
Inventories	(21,032)	(12,394)	(5,933)
Other assets	(6,619)	(5,112)	(9,705)
Accounts payable and accrued expenses	(6,753)	7,507	(22,804)
Other liabilities	(315,462)	(196,640)	(145,759)
Net cash provided by operating activities	355,259	425,267	323,628
Cash flows from investing activities:
Purchases of property, plant and equipment, net	(47,439)	(31,910)	(111,905)
Purchases of held-to-maturity investments	(118,672)	(762,198)	(579,316)
Maturities of held-to-maturity investments	549,576	529,900	527,858
Purchase of investments under the cost method, net	(45,000)	(30,766)
Net cash provided by (used in) investing activities	338,465	(294,974)	(163,363)
Cash flows from financing activities:
Principal payments of debt	(177,800)	(1,320)	(999)
Payments to repurchase common stock	(483,077)	(42,439)	(188,000)
Proceeds from line of credit	140,000
Payments on the line of credit	(140,000)
Proceeds from exercise of stock options	50,168	26,611	16,805
Issuance of stock under employee stock purchase plan	3,329	2,734
Excess tax benefits from share-based compensation	30,845	9,299	3,054
Net cash used in financing activities	(576,535)	(5,115)	(169,140)
Effect of exchange rate changes on cash and cash equivalents	(3,750)	(319)	229
Net increase (decrease) in cash and cash equivalents	113,439	124,859	(8,646)
Cash and cash equivalents, beginning of year	284,258	159,399	168,045
Cash and cash equivalents, end of year	397,697	284,258	159,399
Supplemental cash flow information:
Cash paid for interest	5,453	5,518	5,302
Cash paid for income taxes	195,564	142,140	101,505
Non-cash investing and financing activities:
Acquisitions-non-cash consideration	5,200
Non-cash additions to property, plant and equipment	3,150	9,018	1,820
Issuance of common stock upon conversion of convertible notes	$ 189,311