Fair value measurements Fair value measurements (Summary of assets and liabilities recorded at fair value) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	$ 2,194,748	$ 9,072,646
Equity securities, fair value	0	8,503
Derivatives, assets	14,823	100,475
Fair value, total	2,209,571	9,181,624
Contingent consideration	205,060	135,591
Derivatives, liabilities	65,248	5,710
Fair value, total	270,308	141,301
US treasury securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	81,903	0
Money market funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	1,416,355	7,455,982
Certificates of deposit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	0	1,139,982
US government agencies securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	248,952	0
Municipal debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	12,088	0
Non-U.S. government securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	0	24,741
Corporate debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	352,718	404,989
Residential mortgage-backed and asset-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	82,732	0
Student loan-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	0	46,952
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	1,498,258	7,455,982
Equity securities, fair value	0	8,503
Derivatives, assets	0	0
Fair value, total	1,498,258	7,464,485
Contingent consideration	0	0
Derivatives, liabilities	0	0
Fair value, total	0	0
Level 1 [Member] \| US treasury securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	81,903	0
Level 1 [Member] \| Money market funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	1,416,355	7,455,982
Level 1 [Member] \| Certificates of deposit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	0	0
Level 1 [Member] \| US government agencies securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	0	0
Level 1 [Member] \| Municipal debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	0	0
Level 1 [Member] \| Non-U.S. government securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	0	0
Level 1 [Member] \| Corporate debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	0	0
Level 1 [Member] \| Residential mortgage-backed and asset-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	0	0
Level 1 [Member] \| Student loan-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	0	0
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	696,490	1,544,971
Equity securities, fair value	0	0
Derivatives, assets	14,823	100,475
Fair value, total	711,313	1,645,446
Contingent consideration	0	0
Derivatives, liabilities	65,248	5,710
Fair value, total	65,248	5,710
Level 2 [Member] \| US treasury securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	0	0
Level 2 [Member] \| Money market funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	0	0
Level 2 [Member] \| Certificates of deposit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	0	1,139,982
Level 2 [Member] \| US government agencies securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	248,952	0
Level 2 [Member] \| Municipal debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	12,088	0
Level 2 [Member] \| Non-U.S. government securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	0	0
Level 2 [Member] \| Corporate debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	352,718	404,989
Level 2 [Member] \| Residential mortgage-backed and asset-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	82,732	0
Level 2 [Member] \| Student loan-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	0	0
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	0	71,693
Equity securities, fair value	0	0
Derivatives, assets	0	0
Fair value, total	0	71,693
Contingent consideration	205,060	135,591
Derivatives, liabilities	0	0
Fair value, total	205,060	135,591
Level 3 [Member] \| US treasury securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	0	0
Level 3 [Member] \| Money market funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	0	0
Level 3 [Member] \| Certificates of deposit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	0	0
Level 3 [Member] \| US government agencies securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	0	0
Level 3 [Member] \| Municipal debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	0	0
Level 3 [Member] \| Non-U.S. government securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	0	24,741
Level 3 [Member] \| Corporate debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	0	0
Level 3 [Member] \| Residential mortgage-backed and asset-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	0	0
Level 3 [Member] \| Student loan-backed securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt securities, fair value	$ 0	$ 46,952

Amount of debt securities categorized neither as held-to-maturity nor trading.

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+ Details

- Definition

Amount of equity securities categorized neither as held-to-maturity nor as trading.

+ References

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+ Details

- Definition

Fair value, as of the acquisition date, of potential payments under the contingent consideration arrangement including cash and shares.

+ References

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+ Details