CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
Net income	$ 71,702	$ 48,528	$ 32,042	$ 23,527	$ 72,245	$ 53,649	$ 231,194	$ 22,117	$ 175,799	$ 379,205	$ 40,382
Other comprehensive income (loss), net:
Actuarial loss on defined benefit pension plan, net										(1,034)
Amortization of actuarial loss on defined benefit pension plan, net									17
Reduction of unrealized gain related to cash flow hedging instruments, net											(1,056)
Unrealized gain (loss) on marketable securities, available-for-sale, net									341	(215)	984
Other comprehensive income (loss), net									358	(1,249)	(72)
Comprehensive income									$ 176,157	$ 377,956	$ 40,310