Debt (Tables)

9 Months Ended

Sep. 30, 2015

Debt Disclosure [Abstract]

Schedule of maturities of long-term debt

As of September 30, 2015, contractual maturities of debt for the years ending December 31 are as follows (in thousands):

	Total		2015		2016		2017		2018		2019		Thereafter
1.125% Notes	$	550,000	$	—	$	—	$	—	$	—	$	—	$	550,000
1.625% Notes (1)	301,551		—		—		—		—		—		301,551
	$	851,551	$	—	$	—	$	—	$	—	$	—	$	851,551

(1) The 1.625% Notes have a contractual maturity date in 2044; however, on specified dates beginning in 2018 as described below, holders of the 1.625% Notes may require us to repurchase some or all of the 1.625% Notes, or we may redeem any or all of the 1.625% Notes.

Long term debt

The principal amounts, unamortized discount (net of premium related to 1.625% Notes), and net carrying amounts of the convertible senior notes were as follows:

	Principal Balance		Unamortized Discount		Net Carrying Amount
	(In thousands)
September 30, 2015:
1.125% Notes	$	550,000	$	99,696	$	450,304
1.625% Notes	301,551		26,501		275,050
	$	851,551	$	126,197	$	725,354
December 31, 2014:
1.125% Notes	$	550,000	$	114,670	$	435,330
1.625% Notes	301,551		32,784		268,767
	$	851,551	$	147,454	$	704,097

Debt instruments interest cost recognized

	Three Months Ended September 30,				Nine Months Ended September 30,
	2015		2014		2015		2014
	(In thousands)
Interest cost recognized for the period relating to the:
Contractual interest coupon rate	$	2,772	$	3,132	$	8,316	$	9,732
Amortization of the discount	7,185		6,455		21,257		19,183
	$	9,957	$	9,587	$	29,573	$	28,915