CONSOLIDATED STATEMENTS OF SHAREHOLDERS' EQUITY (USD $) In Thousands, except Share data	Total	Common Stock	Treasury common stock	Additional paid-in capital	Retained earnings	Accumulated other comprehensive income (loss)
Beginning balance at Dec. 31, 2011	$ 2,392,420	$ 1,613	$ (6,343)	$ 1,866,554	$ 373,969	$ 156,627
Beginning balance Shares at Dec. 31, 2011		161,303,000
Issuance of common stock	20,264	13		20,251
Issuance of common stock, shares		1,339,000
Stock-based compensation expense	30,405			30,405
Common dividends declared ($0.16 per share)	(25,981)				(25,981)
Treasury stock issuance			1,583	(1,583)
Other comprehensive income (loss)	(72,718)					(72,718)
Net income	13,002				13,002
Ending balance at Dec. 31, 2012	2,357,392	1,626	(4,760)	1,915,627	360,990	83,909
Ending balance Shares at Dec. 31, 2012		162,642,000
Issuance of common stock	9,289	8		9,281
Issuance of common stock, shares		799,000
Stock-based compensation expense	35,851			35,851
Common dividends declared ($0.16 per share)	(26,129)				(26,129)
Treasury stock issuance			1,123	(1,123)
Other comprehensive income (loss)	(77,673)					(77,673)
Net income	115,722				115,722
Ending balance at Dec. 31, 2013	2,414,452	1,634	(3,637)	1,959,636	450,583	6,236
Ending balance Shares at Dec. 31, 2013	163,441,414	163,441,414
Issuance of common stock	398,607	53		398,554
Issuance of common stock, shares		5,270,000
Stock-based compensation expense	42,834			42,834
Common dividends declared ($0.16 per share)	(26,610)				(26,610)
Treasury stock issuance			549	(549)
Other comprehensive income (loss)	(6,236)					(6,236)
Net income	634,382				634,382
Ending balance at Dec. 31, 2014	$ 3,457,429	$ 1,687	$ (3,088)	$ 2,400,475	$ 1,058,355
Ending balance Shares at Dec. 31, 2014	168,711,131	168,711,131